The effect of insulated combustion chamber surfaces on direct-injected diesel engine performance, emissions, and combustion

The combustion chamber of a single-cylinder, direct-injected diesel engine was insulated with ceramic coatings to determine the effect of low heat rejection (LHR) operation on engine performance, emissions, and combustion. In comparison to the baseline cooled engine, the LHR engine had lower thermal efficiency, with higher smoke, particulate, and full load carbon monoxide emissions. The unburned hydrocarbon emissions were reduced across the load range. The nitrous oxide emissions increased at some part-load conditions and were reduced slightly at full loads. The poor LHR engine performance was attributed to degraded combustion characterized by less premixed burning, lower heat release rates, and longer combustion duration compared to the baseline cooled engine

Methods for heat transfer and temperature field analysis of the insulated diesel, phase 3

Work during Phase 3 of a program aimed at developing a comprehensive heat transfer and thermal analysis methodology for design analysis of insulated diesel engines is described. The overall program addresses all the key heat transfer issues: (1) spatially and time-resolved convective and radiative in-cylinder heat transfer, (2) steady-state conduction in the overall structure, and (3) cyclical and load/speed temperature transients in the engine structure. These are all accounted for in a coupled way together with cycle thermodynamics. This methodology was developed during Phases 1 and 2. During Phase 3, an experimental program was carried out to obtain data on heat transfer under cooled and insulated engine conditions and also to generate a database to validate the developed methodology. A single cylinder Cummins diesel engine was instrumented for instantaneous total heat flux and heat radiation measurements. Data were acquired over a wide range of operating conditions in two engine configurations. One was a cooled baseline. The other included ceramic coated components (0.050 inches plasma sprayed zirconia)-piston, head and valves. The experiments showed that the insulated engine has a smaller heat flux than the cooled one. The model predictions were found to be in very good agreement with the data

Model of piston secondary motion and elastohydrodynamic skirt lubrication

A model of elastohydrodynamic lubrication of reciprocating engine piston skirts was developed in the context of a simulation of piston secondary motions. The piston secondary dynamics, skirt lubrication and skirt elastic deformation problems are simultaneously solved in the calculation. The model can represent both conventional and two-piece articulated pistons and also includes a treatment of wrist pin lubrication. Skirt deformations are calculated using a skirt compliance matrix derived from a finite element model of the piston. The model exercised to calculate piston secondary motions and skirt deformations for a heavy-duty truck diesel piston at various operating conditions. Results show that peak skirt radial deformations can exceed the skirt-liner radial clearance and depend strongly on load. Articulated piston skirt deformations were shown to be significantly larger than those in conventional piston skirts

Integrated modeling of ring pack performance

This paper describes an integrated model developed for the detailed characterization and simulation of piston ring pack behavior in internal combustion engines and the prediction of ring pack performance. The model includes comprehensive and coupled treatments of 1) ring-liner hydrodynamic and boundary lubrication and friction; 2) ring axial, radial and (toroidal) twist dynamics; 3) inter-ring gas dynamics and blowby. The model also includes characterizations of oil transport by rings, as film and of ring-bore conformability. The physics of each of these highly inter-related phenomena are represented by submodels which are intimately coupled to form a design-oriented predictive tool aimed at the calculation of ring film thicknesses, ring motions, land pressures, engine friction and blowby. The paper also describes the results of a series of analytical studies investigating effects of engine speed and load and ring pack design parameters, on ring motions, film thicknesses, inter-ring pressures as well as ring friction and blowby

Experimental and numerical investigation of inter-ring gas pressures and blowby in a diesel engine

Inter-ring gas pressures and blowby in a diesel engine were investigated analytically and compared to experimental data measured at three engine speeds. Coupled simulations of ring dynamics, ring lubrication and inter-ring gas dynamics were carried out using the RINGPAK software, a code for the integrated analysis of ring pack performance and tribology. Inter-ring pressures and ring dynamics are known to have an important effect on the "blowback" mechanism of in-cylinder oil consumption, i.e. that of oil-laden gas flow from the ring lands into the cylinder. Predicted land pressures matched the experimental results very well qualitatively as well as quantitatively. The coupling between ring motions and inter-ring gas pressures and blowby, a key feature of the methodology, was seen to be crucial in obtaining agreement with detailed features of the land pressure data. Ring axial flutter and radial lift and collapse were found to be the second land pressure relief mechanisms which best explain the behavior of measured second land pressure during the power stroke. Simulations were also used to explain the observed effect of top ring bottom keystone angle and helped identify features of the experimental data which are questionable. Some calibration of the simulations was necessary, but consisted of varying ring pack geometrical parameters (end gap dimensions, land volumes), mostly within tolerances. This reveals the very significant effect manufacturing tolerances may have on ring pack performance. Good agreement was also obtained with the blowby mesurements associated with the land pressure data, by seeking correlation with inter-ring pressures only, without otherwise calibrating simulations for a best match of blowby measurements. © Copyright 1993 Society of Automotive Engineers, Inc