نشریه تحقیقات موتور
پیاپی 17 (زمستان 1389)

Several parameters have significant effect on measure and analyzing of cylinder pressure to obtain accurate knock data. Acquisition frequency, number of cycles, transducer location and transducer mounting are measuring parameters. Filtering frequencies, knock windowing, knock model features and threshold values for knock intensity are important analyzing parameters. Effects of these parameters on knock detection and methods for optimal selection are investigated by analyzing test bench datasets. Note that optimalmethods aren’t for special operating conditions and almost cover all operating points of engine. Important parameters for analyzing of transducers’ data, such as digital filtering and Fast Fourier Transformation (FFT), are introduced. FFT determines the main oscillation frequencies and digital filtering omits undesired frequencies.Investigations of test results show that knock is occurred in special frequencies because of acoustic vibration modes, some methods for determining of these frequencies are introduced. It should be mentioned that the main oscillation frequency due to knock is about 8 kHz. Exact determination of these frequencies is important for investigation of filtering and optimal transducer location.

The transient period that lasts from engine starting to achieve engine coolant to its performance temperature is called warm-up. This study tries to decrease the time of warm-up period in a spark ignition engine. To achieving to this goal, at first the coolant thermal operation should be analyzed. For that, engine divided to seven major parts. These components are piston, cylinder block, cylinder head, engine oil, cylinder blockcoolant, cylinder head coolant and radiator coolant. Because warm-up period is a transient period, one of the transient heat transfer analyze methods should be applied. The method that is used in this study is lumped thermal capacitance method. Using heat transfer rules including conduction and convection and ignoring radiation, the thermal equations of mentioned parts are calculated. These equations are nonlinear differential equations that can be arranged in form of a set of differential equations. Because of some complicated nonlinear terms in the differential equations, they can not be solved with analytical methods and so MATLAB software is applied to solve the differential equations set. After solving the differential equations set and finding the temperature changes of major parts, these answers should be validated. To verifying the accuracy of theoretical answers, the answers are compared whit experimental result of engine test that is carried out in IPCO (Irankhodro Powertrain Company). After assuring of the correction and accuracy of theoretical method, some solutions are introduced to reduce the warm-up period. The criterion of warmup period is the thermal operation of engine coolant. So, after applying these solutions, the temperature changes of coolant during warm-up period is calculated for each method and at the end, the advantages anddeficiencies of each solution are discussed.

In this study, the SI engine piston heat transfer is calculated applying three different models for the heat transfer modeling. In the first model, three approximate and constant temperatures are selected for piston, cylinder and cylinder head and determined the in-cylinder gas temperature, pressure and convection coefficients using two-zone combustion model. In the second model for each of the walls (piston, cylinder and cylinder head), the relevant heat transfer equations with two zone model solved considering three unknown temperature. In third model that is the most accurate method, 24 heat transfer equations coupled with the two zone model were solved simultaneously based on resistor-capacitor thermal network model. Eventually, the three model results compared to study their effect on the piston thermal behavior. It has been shown that using of resistor-capacitor model with less number of equations and consequently less time solution is an appropriate method for solving problems of engine heat transfer. The simulations were done by a MATLAB code and the results have been validated with the experimental data of the EF7.TC engine.

This paper presents driving features and their influences on the vehicle’s fuel consumption and exhaust emissions; driving data gathering is performed in real traffic conditions in order to provide the velocity time series. Advance Vehicle Locating (AVL) systems based on GPS technology are used for driving data collection. Then 21 driving features are defined based on vehicle’s velocity time series. After the extraction of features from the driving data, relation between the features is investigated in order to determine independent features. The influence of the selected features on vehicle’s fuel consumption and pollutant emissions is then studied using computer simulations. The Advisor software is utilized here for two types of vehicles, conventional SAMAND and hybrid SAMAND (HEV), simulation results are compared with test results in somecases. Finally the most effective driving features are determined by a total index and superior features are identified and presented as the result of this study. These superior features can be used in traffic condition clustering, driving cycle development, traffic condition clustering and intelligent HEV control.

This article proposes a new method on recognition of driving style, Roadway Type, and level of congestion based on some of information available in electronic control unit (ECU) of vehicles. Vehicle speed, engine speed, indicatory torque, acceleration pedal position, brake activity, and clutch pedal are used to achieve this goal. Driving style is the driver's behavior that can be variable according to driver's personal characteristics and level of congestion in the road. This paper is part of the research on «Driving Pattern Recognition and Traffic Identification in Tehran for Control of Hybrid Vehicles» that is supported byIrankhodro Powertrain Corporation (IPCO). In the proposed method, Neural Networks are used to classify the Driving Style into three categories: calm, normal, and aggressive; based on the features extracted from ECU information. Data collected in this research in calm, normal, and aggressive classes in collaboration with IPCO in the real traffic conditions. Results show Driving Style can be recognized with neural network with high performance, although Roadway Type and level of congestion didnt recognized well. Correct classification rate that reached are 70% for Roadway Type and level of congestion, and above 90% for Driving Style. The results attained in this research have many profits and can be used for control of vehicles (especially hybrid electric vehicles) in future works.

Biodiesel can be used easily as an alternative fuel in diesel engine and is environmentally friendly. In the present work for prediction of combustion process in a low speed diesel engine (M8/1 Lister), a single-zone combustion model (Whitehouse-Way) was used. This model was verified by experimental data. Predicted values of cylinder pressure and heat release rate from this modeling showed good agreement with corresponding experimental data. Also, the results of the engine short time tests, showed with increasing biodiesel percentage up to 20 volumetric, same properties such as pressure peak in combustion chamber, exhaust engine temperature, ignition delay, engine speed, brake and indicatory efficiency were increased. Due to combustion quality improvement, CO and UHC emissions were decreased, but NOx increased through higher combustion temperature and consequently higher pressure. Brake specific fuel consumption was minimum in compound which is economically very important.

Cylinder head is one of the critical components of diesel engine that is subject to different thermal and mechanical loadings. One of the cylinder head design targets is durability and high fatigue life of this part. Thermal loading is the major loading of cylinder head in term of fatigue life assessment because leads to thermal stress and low cycle fatigue. Therefore, the study of the effect of thermal boundary conditions on the temperature distribution of cylinder head will assist cylinder head designer and is necessary part of cylinder head design. In this study, the effects of thermal boundary conditions, due to combustion gases and cooling gallery, at different engine operating conditions on the temperature distribution of a heavy duty diesel engine cylinder head are investigated. Also, the influences of other thermal boundary conditions on the temperature distribution of cylinder head at the critical regions are studied.