The Investigation of the Valve Spring Stiffness Influence on the Thermal Contact Conductance Between the Exhaust Valve and Its Seat

Abstract

AbstractAn experimental study for estimation of thermal contact conductance between an exhaust valve and its seat in an internal combustion engine has been accomplished. In this study, an actual exhaust valve and its seat are utilized in a setup. Several experiments under different conditions have been conducted to acquire desired data. In addition, an inverse heat conduction problem for estimating both constant and periodic thermal contact conductance has been solved using the conjugate gradient method (CGM) with adjoint problem for function estimation, which converges very rapidly and is not as sensitive to the measurement errors. The influence of the contact pressure upon the thermal contact conductance is investigated by using valve springs with different stiffness. The results show that the thermal contact conductance increases as the stiffer valve spring is used. The results obtained with CGM and the linear extrapolation ones are in good agreement. ACKNOWLEDGMENTSThe authors thank the Iran Khodro Power Train Company for its financial support to build the experimental setup and its measurement equipment.NOMENCLATURECGM=conjugate gradient methodcp=specific heat, J/kg-Kd=direction of descent, W/m2-Ke=roughness, mH=Hilbert space of square-integrable functionshc=thermal contact conductance, W/m2-KI=maximum number of parametersK=spring stiffness, N/mk=thermal conductivity, W/m-KL=length, mN=number of sensorsp=independent variableq=heat flux, W/m2R=result functionS=objective function, K2T=temperatures, KT0=constant temperature at x = 0, KTi=initial temperature, Kt=time, sY=measured temperatures, Kx=Cartesian spatial coordinateGreek Symbolsα=thermal diffusivity, m2/sβ=search step sizeγ=conjugation coefficientΔ=variationΔT=sensitivity function, Kδ(.)=Dirac delta functionλ=Lagrange multiplier satisfying the adjoint problemρ=density, kg/m3σ=standard deviationω=error in measuring parameter∇S(.)=gradient directionSubscripts1=seat region2=valve regionc=contactf=finali=ith parameterj=jth sensork=kth sensorm=meanmeas=measurement locationSuperscripts0=initial guessk=iteration numberAdditional informationNotes on contributorsMohammad Hassan ShojaeefardMohammad Hassan Shojaeefard is a professor of mechanical engineering at Iran University of Science and Technology (IUST). He is head of the Automotive Engineering School and Research Center at IUST. He is also head of the Iran Society of Automotive Engineering. Since his graduation from University of Birmingham, he has been working in several fields, such as turbomachinery, thermal contact, and internal combustion engines.Vahid Mousapour KhaneshanVahid Mousapour Khaneshan is a Ph.D. student at Iran University of Science and Technology (IUST), School of Mechanical Engineering, and under the supervision of Prof. Shojaeefard. He received his master's degree in mechanical engineering in 2009. He has been working on the thermal contact and solar air heating. He is currently working on intake valve deposits.Mohammad Mazidi SharfabadiMohammad Mazidi Sharfabadi is an Assistant Professor at Optimization and Development of Energy Technologies Division of Research Institute of Petroleum Industry (RIPI). He received his Ph.D. degree from School of Mechanical Engineering of Iran University of Science and Technology (IUST) in 2013. He had been working experimentally and numerically on the thermal contact between an exhaust valve and its seat in an internal combustion engine. His fields of interest are sustainable and renewable energy, inverse heat transfer and thermal contact.