Method for Determining Instantaneous Temperature at the Surface of Combustion Chamber Deposits in an HCCI Engine

Abstract

Homogeneous charge compression ignition (HCCI) combustion is widely regarded as an attractive option for future high efficiency gasoline engines. HCCI combustion permits operation with a highly dilute, well mixed charge, resulting in high thermal efficiency and extremely low NOj, and soot emissions, two qualities essential for future propulsion system solutions. Because HCCI is a thermokinetically dominated process, full understanding of how combustion chamber boundary thermal conditions affect the combustion process are crucial. This includes the dynamics of the effective chamber wall surface temperature, as dictated by the formation of combustion chamber deposits (CCD). It has been demonstrated that, due to the combination of CCD thermal properties and the sensitivity of HCCI to wall temperature, the phasing of autoignition can vary significantly as CCD coverage in the chamber increases. In order to better characterize and quantify the influence of CCDs, a numerical methodology has been developed which permits calculation of the crank-angle resolved local temperature profile at the surface erf a layer of combustion chamber deposits. This unique predictor-corrector methodology relies on experimental measurement of instantaneous temperature underneath the layer, i.e., at the metal-CCD interface, and known deposit layer thickness. A numerical method for validation of these calculations has also been devised. The resultant crank-angle resolved CCD surface temperature and heat flux profiles both on top and under the CCD layer provide valuable insight into the near wall phenomena, and shed light on the interplay between the dynamics of the heat transfer process and HCCI burn rates.There is a substantial body of work on CCD regarding conventional SI and CI engines, but to date, apart from previous results directly related to the work shown in this paper [14,15], there is little previously published work addressing deposits in an HCCI Journal of Engineering for Gas Turbines and Power

Assessing the capability of conventional in-cylinder insulation materials in achieving temperature swing engine performance benefits

“…Heat transfer from the combustion gas was dictated by the Woschni convection correlations, while heat transfer between structures and to thermal sinks (oil and coolant) was specified through individual convection coefficients. Calibration of these convection coefficients was performed utilizing measurements in the literature [25][26][27][28] in addition to unique measurements taken through similar means in the experimental study. More details on this model are in prior publications by Andruskiewicz et al 1…”

Analysis of the effects of wall temperature swing on reciprocating internal combustion engine processes

“…Piston and head surface temperatures throughout the cycle could be compared to experimental data taken by Guralp et al 22 The original measurements of multiple piston and a single head location were obtained for four data points and were processed using the same experimental data analysis routines used to calibrate the thermodynamic model for consistency. Woschni's heat transfer correlation was modified according to the method described in Chang et al 23 to ensure applicability to homogeneous charge compression ignition (HCCI).…”

Thermal Characterization of a Gasoline Turbocharged Direct Injection (Gtdi) Engine Utilizing Lean Operation and Exhaust Gas Recirculation (Egr)

“…Previous studies have shown that deposits on combustion chamber surfaces can have a significant effect on the response of surface thermocouples [23,24]. As the deposit layer increased in thickness, it added thermal mass and decreased the response time of the sensor.…”

“…The effects of deposits on instantaneous temperature and heat flux measurements in HCCI engines have been studied extensively by Güralp et al [23,24]. They utilized coaxial thermocouples with a vacuum deposited surface junction to measure piston surface temperatures.…”

“…While studying the effect of deposits on surface temperature measurements in HCCI engines, Güralp et al [23,24] noticed a signature of liquid fuel spray impingement on the piston surface. On the thermocouples located close to the fuel injector tip, a sharp decrease in surface temperature was observed under certain engine conditions.…”