Automotive Science and Engineering

In this study it has been tried, to compare results and convergence rate of sensitivity analysis and conjugate gradient algorithms to reduce fuel consumption and increasing engine performance by optimizing the timing of opening and closing valves in XU7/L3 engine. In this study, considering the strength and accuracy of simulation GT-POWER software in researches on the internal combustion engine, this software has been used. In this paper initially all components of engine have been modeled in GT-POWER. Then considering the experimental result, results confirmed the accuracy of the model. After model verification, GT-POWER model with MATLAB-SIMULINK are coupled each other, to control the inputs and the outputs by sensitivity analysis and conjugate gradient algorithms. Then the results compared with experimental results of initial engine too. The results indicated that optimal valve timing significantly reduced brake specific fuel consumption and when is used variable valve system for opening and closing angle of intake and exhaust valves, the mean improvement percentage in brake specific fuel consumption from sensitivity analysis is nearly 5.87 and from conjugate gradient is about 6.69. too, for example with increasing engine speed late closing intake valve causes optimized brake specific fuel consumption and from 3500rpm this trend stops and in 4000rpm and 4500rpm early closing of intake valve results in more optimized brake specific fuel consumption. Then up to 6000rpm again late closing of valve would be favorable. Also results indicated that convergence rate of conjugate gradient algorithm to reaching the optimal point is more than sensitivity analysis algorithm.

Thermal Contact Conductance (TCC) between an exhaust valve and its seat is one of the important parameters to be estimated in an internal combustion engine. An experimental study presented here to acquire temperature in some interior points to be used as inputs to an inverse analysis. An actual exhaust valve and its seat are utilized in a designed and constructed setup. Conjugate Gradient Method (CGM) with adjoin problem for function estimation is used for estimation of TCC. The method converges very rapidly and is not so sensitive to the measurement errors. Contact frequency is one the factors which have a significant influence on TCC. The results obtained from current inverse method as well as those obtained from linear extrapolation method show that the thermal contact conductance decreases as the contact frequency increases. The results obtained from both sets of results are also in good agreement.

Thermal Contact Conductance (TCC) between an exhaust valve and its seat is one of the important parameters to be estimated in an internal combustion engine. An experimental study presented here to acquire temperature in some interior points to be used as inputs to an inverse analysis. An actual exhaust valve and its seat are utilized in a designed and constructed setup. Conjugate Gradient Method (CGM) with adjoin problem for function estimation is used for estimation of TCC. The method converges very rapidly and is not so sensitive to the measurement errors. Contact frequency is one the factors which have a significant influence on TCC. The results obtained from current inverse method as well as those obtained from linear extrapolation method show that the thermal contact conductance decreases as the contact frequency increases. The results obtained from both sets of results are also in good agreement.