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

A STUDY OF HEAT TRANSFER DUE TO A DECAYING SWIRLING FLOW IN A CYLINDER WITH CLOSED ENDS

Heat transfer due to an axisymmetric swirling flow in a cylinder with closed ends was studied. Argon gas was introduced into an evacuated cylinder to establish an axisymmetric swirling flow. Gas temperatures, local heat fluxes, pressure and velocities were measured for the next 500 msec as the flow field decayed. It was observed that the normalized turbulence intensity field is a weak function of time. The decaying velocity field retains its spatial distribution with the passage of time as do the local heat fluxes at the planar wall. The global Nusselt number correlates with a Reynolds number based on the half radius velocity. The exponent of the Reynolds number in that correlation varies from(\u27 (TURN)).8 for high aspect ratios to (\u27(TURN)).5 for low aspect ratio cylinders. It is concluded that the flow field is quasi-steady for aspect ratios greater than two where the exponent remains constant at 0.8

1D simulation models for aftertreatment components

This book is an attempt to provide a description of the most significant and recent achievements in the field of 1D engine simulation models and coupled 1D-3D modeling techniques, including 0D combustion models, quasi-3D methods, and some 3D model applications

Modeling NOx Storage and Reduction for a Diesel Automotive Catalyst Based on Synthetic Gas Bench Experiments

To comply with stringent NO x emission regulations, automotive dies el engines require advanced aftertreatment catalytic systems, such as lean NO x traps (LNTs). Considering that test bench and chassis dyno experimental campaigns are costly and require a vast use of resources for the generation of data; therefore, reliable and computationally e ffi cient simulation models are essential in order to identify the most promising technology mix to satisfy emission regulations. In the literature, a large number of simulation models for LNT kinetics can be found, realized for laboratory-scale samples and validated over synthetic gas bench (SGB) experimental tests, while full-size models validated over engine-dyno driving cycle data, crucial for industrial applications, are missing. In the current work, a simulation model of an LNT device is built to predict NO x storage and reduction, starting from SGB laboratory tests and fi nally validated over driving cycle data. The experiments including light-o ff , NO x storage and reduction (NSR), and oxygen storage capacity (OSC) characterization, were performed on a laboratory-scale sample extracted from a full-scale monolith. Light-o ff tests have been conducted under a temperature ramp cycle from 120 ° Cto 380 ° C, while OSC and NSR tests were performed under isothermal conditions at fi ve temperature levels, ranging from 150 ° C to 400 ° C. OSC tests were performed to characterize oxygen storage capacity of ceria sites and water gas shift (WGS) reaction over the precious metals by controlling inlet species concentrations with periodic lean/rich pulses. NSR experiments were then performed by alternating a lean inlet composition to reproduce adsorption/desorption of NO x with a rich inlet composition feed with three reductants (H 2 , CO, and C 3 H 6 ) to replicate NO x reduction reactions. A global kinetic scheme was de fi ned by means of a one-dimensional (1D) engine simulation fl uid-dynamic code, GT-SUITE, to model oxidation reactions (CO, HC, NO), NO x adsorption/desorption, oxygen storage and NO x reduction reactions. The kinetic parameters were obtained using Arrhenius plots with the aim to minimize the error between simulated and experimental NO x , reductants, N 2 O and NH 3 concentrations, reaching a satisfactory agreement with measurements

Examining the role of flame topologies and in-cylinder flow fields on cyclic variability in spark-ignited engines using large-eddy simulation

In this work, we have studied cycle-to-cycle variation in a spark-ignited engine using large-eddy simulation in conjunction with the G-equation combustion model. A single cylinder of a four-cylinder port-fueled spark-ignited engine was simulated. A total of 49 consecutive full cycles were computed. The operating condition studied in this work is stoichiometric and stable and represents a load of 16 bar brake mean effective pressure and an engine speed of 2500 r/min. The computational fluid dynamics simulation shows good agreement in terms of in-cylinder pressure prediction with respect to the experiments and is also able to capture the range of cycle-to-cycle variation observed in experiments. Furthermore, neither the simulation nor the experiments show any distinguishable pattern in the sequence of high and low cycles. We numerically decoupled the effects of variations in equivalence ratio fields and velocity fields to isolate the effects of differences in the velocity field and differences in the equivalence ratio field on flame development and propagation. Based on this study, we inferred that for this engine, under the operating conditions studied, the differences in burn rates can be attributed to the differences in the velocity flow-field in the region around the spark gap during ignition. We then performed an analysis to identify the correlation between peak cylinder pressure and flame topologies over all the simulated cycles. We found that high cycles (higher peak cylinder pressure values) are strongly correlated to flatter flame volume shapes (flattened in the piston-to-head direction) and volumes that are more symmetric about the ignition axis. In addition, these kinds of flame volumes were found to correlate well with lower values of prior-to-ignition velocity going from the intake to the exhaust side (mean flow caused by tumble) at the spark and also higher values of prior-to-ignition velocity in the piston-to-head direction