Roy James Primus

Multidimensional Modeling and Validation of Dual-Fuel Combustion in a Large Bore Medium Speed Diesel Engine

High fidelity, three-dimensional CFD was used to model the flow, fuel injection, combustion, and emissions in a large bore medium speed diesel engine with different levels of natural gas substitution. Detailed chemical kinetics was used to model the complex combustion behavior of the premixed natural gas, ignited via a diesel spray. The numerical predictions were compared against measured multiple cycle pressure data, to understand the possible factors affecting cyclic variation in experimental data. Under conditions with high natural gas substitution rates, diesel was injected much earlier than firing-TDC. This additional mixing time allowed the active radicals from diesel dissociation to initiate combustion from the cylinder wall and propagate inwards. 0%, 60%, and 93% natural gas substitution rates (by energy) were tested in this study to develop computational capabilities needed to accurately model and understand the underlying physics. Several innovative computational methods such as adaptive mesh refinement (which automatically refines and coarsens the mesh based on the existing solution parameters), and multi-zoning (which groups chemically similar cells together to reduce combustion calculation time) were utilized to obtain accurate predictions at a lower computational cost. Important engine emissions such as NOx, CO, unburnt HC, and soot were predicted numerically and compared against measured engine data.Copyright

Cycle to Cycle Variation Study in a Dual Fuel Operated Engine

This research used resources of the KAUST Supercomputing Laboratory located at King Abdullah University of Science and Technology, Saudi Arabia. Components of this work were supported by the U.S. Department of Energy, Vehicle Technologies Office.

An Assessment of the Relative Benefits of Miller Cycle and Turbocompounding on a Medium Speed Diesel Engine Using Second Law Analysis

The relative benefit of a power turbine as a means of exhaust energy recovery (i.e., turbocompounding) being used in conjunction with altered intake valve closure timing (Miller cycle) on a medium speed diesel engine has been investigated. An assessment of the impact of these different engine architectures on the various loss mechanisms has been performed using second law analysis. The Miller and turbocompounding cycle modification as well as the combination of the two features were studied and their relative benefits are compared and discussed. Results show the corresponding decrease in effective compression ratio achieved with Miller cycle leads to lower pre-turbine exhaust availability, which decreases the potential benefit of turbocompounding.Copyright

SFC Benefit With Split Injection in Two-Stroke Diesel Engine

The influence of split-injection on engine performance is studied using system and in-cylinder simulation of a two-stroke medium speed diesel engine. System level models for the engine and fuel system and a multi-dimension CFD model for the combustion chamber were developed and calibrated with experimental data. Calibration of these models from the available test data is discussed and calibration results are presented. The SFC and NOx predictions show good sensitivity to injection timing variation. These calibrated models were then used to simulate split injection through the modification of the fuel injector. Split injection achieved through this modification results in fuel savings while maintaining same NOx levels.Copyright

Integration of System and Detailed CFD Models for IC Engine Applications

Stringent IC engine tailpipe emission regulations are being enforced worldwide. To meet the emission norms various emission reduction strategies are explored in conjunction with the fuel consumption improvements. To achieve these goals, modeling of engine system for combustion and emission plays a major role in minimizing the development cost and time. The successful application of combustion and emission modeling depends on the response, accuracy and run-time of the models being used. System level models are generally used to study and optimize the full IC engine system. These models have low runtime (2–10 mins) but are limited in their ability to describe and respond to the geometry and physics of complex fluid dynamics, combustion and emissions. Detailed CFD models are used for these areas but have long runtimes (8–40 hours). The procedure for developing and calibrating commercially available system and in-cylinder CFD software models are explained. Also the integration of these models to minimize the overall runtimes is described in detail.Copyright

The Evolution of Diesel Engine Performance Prediction

Thermodynamic system performance modeling has become an integral part of the engine development process. The modeling tools used for this type of analysis have evolved from fairly simple calculations of limited scope into detailed simulations with ever-increasing complexity. These analytical tools are based on the combination of basic concepts, physical phenomena and experimental correlations. As with other categories of analysis, their evolution has also been closely coupled with the advances in computer technology.This document provides a historic view of thermodynamic system simulation and revisits some of the developments in modeling techniques, engine measurements, data acquisition systems and computer hardware that have contributed to the understanding of engine performance prediction.© 2014 ASME

Aftertreatment System Integration on a Tier 2 Evolution Locomotive: Analysis and Field Test Results

Results of an effort to integrate an aftertreatment system for the simultaneous reduction of NOx and PM emissions on a Tier 2 Evolution Locomotive are presented. The paper provides detail on the solution that was realized to meet packaging constraints and also highlights aftertreatment performance limitations that resulted from these design decisions. Analysis results showing the predicted impact on engine performance are presented and compared to results obtained from field testing of the integrated system.Copyright

Comparison of Alternative EGR Systems for a Medium Speed Diesel Engine

Meeting future regulations for diesel engine NOx emissions with in-cylinder solutions will require a high rate of exhaust gas recirculation (EGR). For medium speed diesel engines, the exhaust manifold pressure is typically lower than that of the intake manifold, necessitating a rise in the exhaust gas pressure for exhaust flow to be introduced into the intake manifold. In this study, four high-pressure EGR engine concepts are investigated as a means to meet EPA Tier 4 NOx emissions. These concepts include a system with an EGR pump, one with a power turbine downstream of the turbocharger (i.e., turbocompounding), one with dedicated donor EGR cylinders and the use of a backpressure valve. For each system, an optimum set of parameters that included intake valve timing, intake manifold pressure, and fuel injection timing were found that satisfy the emissions requirements while staying within the mechanical limits of the system. From an efficiency perspective, the turbocompound system is generally superior, followed by the donor cylinder concept. The EGR pumping system typically has lower overall efficiency due to the compressor power requirement and the use of a backpressure valve, representing the baseline for comparison, produced the lowest system efficiency.Copyright

An Investigation in Improving the Exhaust Management Process on Miller Cycle and Turbocompounding

A reduction in diesel engine fuel consumption at a constant emissions level can be achieved by various means. A power turbine as a means of waste heat recovery (i.e., turbocompounding) and altered intake valve closure timing (Miller cycle) are two such mechanisms. Each of these technologies act as a means of improving the expansion process of the combustion gases, requiring reduced fueling for the same work extraction. When these embodiments are typically implemented, the timing of the exhaust valve opening is maintained. However, optimization of the timing of the exhaust valve opening presents the potential for further improvement in the expansion process. Variations in the exhaust valve opening timing will be investigated for Miller and turbocompounding cycles as well as the combination of the two features. Results will be shown to quantify the impact these variations have in system efficiency. Second law analysis will be used to show how these variations in engine configurations impact individual loss mechanisms. Finally, comparisons will be made to show the relative differences between Miller cycle and turbocompounding with and without optimization of the exhaust valve timing.Copyright

Investigation of Injection Pressure Effects on Medium Speed Diesel Engine Emissions

As with most internal combustion engines, the locomotive diesel is subjected to increasingly stringent regulatory emissions standards. Currently, diesel electric freight locomotives are regulated by the Tier 1 emission standards that went into effect January 1, 2002 as ruled by the United States Environmental Protection Agency (EPA). Beginning January 1, 2005 the US EPA Tier 2 diesel locomotive emissions standards will become effective. To achieve the new emissions standards an extensive engine development program was initiated. This paper will present a portion of the development conducted on a single cylinder engine (SCE) investigating the effects of injection pressure on emissions. The experimental results are presented with a discussion of the possible mechanisms leading to the results with supporting evidence from existing literature and analysis. This paper will focus on the effect of injection pressure as generated by pump capacity and nozzle cup hydraulic flow.Copyright