The conjugate gradient method using two search step sizes is used to solve the inverse problem of simultaneously estimating the periodic thermal contact conductance, hc(t), and the heat transfer coefficient of the exhaust gases, hg(t), between the exhaust valve and seat in an internal combustion engine. The importance of the determination of hc(t) and hg(t) lie in that they are the critical factors for designing the cooling system and the insulation of the exhaust valve. The inverse analysis is based on the temperature measurements taken from the sensors placed in both the valve and seat regions during the transient process of operation. In this study two unknown timewise‐varying functions hc(t) and hg(t) are to be estimated at the same time, thus two search step sizes with each one corresponding to each unknown function are derived. The results show that the CPU time for the inverse solutions using two search step sizes are greatly reduced than using just one search step size1 for the determination of two unknowns, besides, it also shows that the inverse solutions are reliable even when the measurement errors are considered. The advantage of the conjugate gradient method is that no a priori information is needed on the variation of the unknown quantities, since the solution automatically determines the functional form over the domain specified. The successful development of the present technique can be applied to any kind of two‐dimensional periodic contact problems, such as the determination of a two‐dimensional contact conductance problem2 and the temperature or heat flux behaviour on the inside wall of internal combustion engines3.
|Number of pages||20|
|Journal||International Journal for Numerical Methods in Engineering|
|Publication status||Published - 1995 Mar 15|
All Science Journal Classification (ASJC) codes
- Numerical Analysis
- Applied Mathematics