Investigation of the temperature oscillations in the cylinder walls of a diesel engine with special reference to the limited cooled case

Abstract

SUMMARYThis work investigates the interesting phenomenon of the temperature (cyclic) oscillations in the combustion chamber walls of a diesel engine. For this purpose, a comprehensive simulation code of the thermodynamic cycle of the engine is developed taking into account both the closed and the open parts of it. The energy and state equations are applied, with appropriate combustion, gas heat transfer, and mass exchange with the atmosphere sub-models, to yield cylinder pressure, local temperatures and heat release histories as well as various performance parameters of the engine. The model is appropriately coupled to a wall periodic conduction model, which uses the gas temperature variation as boundary condition throughout the engine cycle after being treated by Fourier analysis techniques. It is calibrated against measurements, at various load and speed conditions, from an experimental work carried out on a direct injection (DI), naturally aspirated, four-stroke, diesel engine located at the authors' laboratory, which has been reported in detail previously. After gaining confidence into the predictive capabilities of the model, it is used to investigate the phenomenon further, thus providing insight into many interesting aspects of transient engine heat transfer, as far as the influence that engine wall material properties have on the values of cyclic temperature swings. These swings can take prohibitive values causing high wall thermal fatigue, when materials of specific technological interest such as thermal insulators (ceramics) are used, and may lead to deterioration in engine performance.

Study of the Transient Operation of Low Heat Rejection Turbocharged Diesel Engine Including Wall Temperature Oscillations

“…The detailed formulation of the time-periodic heat conduction problem has been analyzed in detail by Rakopoulos et al [26,27]. In this paper, only a brief outline will be given highlighting the basic equations applied.…”

“…Response of various engine parameters to an increase in load (unless otherwise noted, the cylinder wall is cast iron) He argued that an increased level of insulation led to some kind of 'deterioration' of the combustion process by shifting a larger part of the fuel burning into the diffusion phase, i.e. later in the cycle [26]. Schwartz et al [40], extending the results of Alkidas, concluded that an improved time phasing of premixed and diffusion burning must be accomplished if a desirable heat release is to be derived in a LHR engine, as the heat release pattern exhibits a great sensitivity to even small changes.…”

“…Some researchers of steady-state LHR engine operation have reported a decrease in the bmep with increasing insulation [9,26]. This conflicting behavior of bmep development, when comparing steady-state and transient tests, can be explained if one looks deeper into the respective principles.…”

“…Wong et al [10] investigated the interdependence between engine efficiency and temperature swings amplitude. Rakopoulos et al [26,27] focused on a naturally aspirated diesel engine and included the effect of silicon nitride insulation, providing comparative results for the various insulation schemes applied. Yamada et al [28] expanded the temperature swings analysis to cover even the case where the deposit on the cylinder wall affects the gas-to-cylinder heat transfer.…”

Review of Thermodynamic Diesel Engine Simulations under Transient Operating Conditions

“…Diesel engine simulation has contributed enormously during the last 40 years towards new evaluation and development [3][4][5][6][7][8][9][10][11]. Thermodynamic cycle simulations give access to data that otherwise can only be measured with complicated and costly techniques.…”