Rolf Reitz

University of Wisconsin–Madison | UW · Department of Mechanical Engineering

div class="section abstract"> The possibility to operate current diesel engines in dual-fuel mode with the addition of an alternative fuel is fundamental to accelerate the energy transition to achieve carbon neutrality. The simulation of the dual- fuel combustion process with 0D/1D combustion models is fundamental for the performance prediction, bu...

div class="section abstract"> We propose a novel dual-fuel combustion model for simulating heavy-duty engines with the G-Equation. Dual-Fuel combustion strategies in such engines features direct injection of a high-reactivity fuel into a lean, premixed chamber which has a high resistance to autoignition. Distinct combustion modes are present: the D...

The introduction of downsized, turbocharged Gasoline Direct Injection (GDI) engines in the automotive market has led to a rapid increase in research on Low-speed Pre-ignition (LSPI) and super-knock as abnormal combustion phenomena within the last decade. The former is characterized as an early ignition of the fuel–air mixture, primarily initiated b...

In model-based combustion simulations, laminar flame speed (LFS) is a vital parameter for predicting spark-ignited (SI) turbulent combustion, which is unstable under ultra-lean mixtures. Accurate predictions of ultra-lean combustion require a proper LFS correlation. This work proposes a novel LFS equation for a 5-component gasoline surrogate to ref...

Diesel piston-bowl shape is a key design parameter that affects spray-wall interactions and turbulent flow development, and in turn affects the engine’s thermal efficiency and emissions. It is hypothesized that thermal efficiency can be improved by enhancing squish-region vortices as they are hypothesized to promote fuel-air mixing, leading to fast...

The adverse environmental impact of fossil fuel combustion in engines has motivated research towards using alternative low-carbon fuels. In recent years, there has been an increased interest in studying the combustion of fuel mixtures consisting mainly of hydrogen and carbon monoxide, referred to as syngas, which can be considered as a promising fu...

Various successful applications have proven the reliability of using multi-dimensional CFD tools to assist in diesel engine research, design, and development. Those applications can be categorized as follows: using CFD tools to reveal details about invisible (or technically difficult and/or costly) in-cylinder processes of diesel combustion, so tha...

With the exponentially increasing computational power of modern computers, multi-dimensional computational fluid dynamics (CFD) has found more and more applications in diesel engine research, design, and development since its initiation in the late 1970s. Enhanced understanding of the physical processes of diesel combustion and correspondingly impr...

Recent research on thermal reciprocating engines has focused on the influence of lubricant oil on the combustion process, which can lead to highly unde-sired super-knock events. Low-Speed Pre-Ignition (LSPI) events severely limit the further development of Direct Injection Spark Ignition Engines (DISI), preventing high effi-ciencies from being achi...

While forced induction strategies such as turbocharging can increase the power output and extend the load limit of engines operating on low temperature combustion strategies such as reactivity controlled compression ignition, the low exhaust enthalpy prevalent in these strategies requires the use of high backpressures to attain high turbocharger ef...

Reactivity-controlled compression ignition (RCCI) is a promising energy conversion strategy to increase fuel efficiency and reduce nitrogen oxide (NOx) and soot emissions through improved in-cylinder combustion process. Considering the significant amount of conducted research and development on RCCI concept, the majority of the work has been perfor...

Low Temperature Combustion (LTC) strategies are most promising to simultaneously reduce oxides of nitrogen (NO x) and soot emissions from diesel engines along with offering higher thermal efficiency. Commercial wide spread implementation of diesel LTC strategies requires several challenges to be addressed, including lack of precise ignition timing...

Low temperature combustion strategies have demonstrated high thermal efficiency with low pollutant emissions (e. g., oxides of nitrogen and particulate matter), resulting from reduced heat transfer losses and lean air-fuel mixtures. One such advanced compression ignition combustion strategy, Reactivity Controlled Compression Ignition (RCCI), has de...

The production of increasingly clean engines has become imperative. More stringent regulations for internal combustion engines are constantly proposed, and recent number-based regulations have become a new challenge, since historically only a mass-based regulation needed to be met. It is known that soot particles detectable at the exhaust of an eng...

An Equilibrium Phase (EP) spray model for simulating high-pressure diesel fuel injection has recently been proposed, which is based on a local phase equilibrium assumption and jet theory. In this model, spray vaporization is assumed to be a mixing-controlled equilibrium process, while the non-equilibrium processes of droplet breakup, collision and...

The importance of radiative heat transfer in internal combustion engines is studied using Computational Fluid Dynamics (CFD) simulations. The Discrete Ordinates Method (DOM) is implemented and a Spherical surface Symmetrical equal Dividing angular quadrature with order of 2 is selected for the angular direction discretization with <4% relative erro...

The internal combustion engine has been a major power plant in transportation and industry, and demands continuously advanced technologies to improve its performance and fuel economy, and to reduce its pollutant emissions. Liquid fuel injection is critical to the combustion process in both compression ignition (CI) diesel engines and gasoline direc...

An Equilibrium Phase (EP) spray model has been recently proposed for modeling high-pressure diesel fuel injection, which is based on jet theory and a phase equilibrium assumption. In this approach, the non-equilibrium processes of drop breakup, collision and surface vaporization are neglected, assuming that spray vaporization is a mixing-controlled...

We developed two approaches to speed up combustion chemistry simulations by reducing the amount of time spent computing exponentials, logarithms, and complex temperature-dependent kinetics functions that heavily rely on them. The evaluation of these functions is very accurate in 64-bit arithmetic, but also slow. Since these functions span several o...

A reaction mechanism, suitable for simulating the lubricant oil influence on the combustion process of gasoline-like fuels, is developed. The proposed work is motivated by evidences reported in the literature highlighting that lubricant oil droplets can be the most likely inducer of pre-ignition phenomena, as well as the fact that lubricant oil can...

The objective of the present work is to provide an exhaustive characterization of size distributions and number density of the particles emitted from a modern EURO-VI heavy-duty 4-cylinder engine, fueled with compressed natural gas. To achieve this goal, a wide range of operating conditions (for a total of 60 operating points) were investigated dur...

The exergy destruction sources of different engine combustion regimes are investigated. The results indicate that chemical reaction is the largest sources of exergy destruction. Although the exergy destruction due to chemical reaction in conventional diesel combustion (CDC) engines is the lowest, its total exergy destruction is the largest. The tra...

Real gas effects on combustion and emissions in internal combustion engines are investigated using three-dimensional computational fluid dynamics. The Peng–Robinson equation of state is implemented to describe pressure–volume–temperature relationships and to calculate thermodynamic properties and relevant partial derivatives. Four facilities are mo...

High-pressure fuel injection impacts mixture preparation, ignition and combustion in engines and other applications. Experimental studies have revealed the mixing-controlled and local phase equilibrium characteristics of liquid vaporization in high injection pressure diesel engine sprays. However, most computational fluid dynamics models for engine...

This work studied how in-cylinder flow structure is affected in a light-duty, swirl-supported diesel engine when equipped with three different piston geometries: the first two featuring a conventional re-entrant bowl, either with or without valve cut-outs on the piston surface and the third featuring a stepped-lip bowl. Particle image velocimetry e...

Natural gas is increasingly used as an alternative to petroleum fuels in internal combustion engines and industrial power plants because of its smaller environmental effects, as well as for economic reasons. Many applications, such as the spark-ignition engine simulations and the design of burners, require an accurate calculation of its laminar fla...

In natural gas/diesel Reactivity Controlled Compression Ignition (RCCI) engines, the large reactivity gradient between the two fuels is beneficial in achieving lower pressure rise rate and peak pressure values at high loads. However, by using natural gas, combustion efficiency and engine performance suffer at low loads due to its lower reactivity a...

The laminar flame speed plays an important role in spark-ignition engines, as well as in many other combustion applications, such as in designing burners and predicting explosions. For this reason, it has been object of extensive research. Analytical correlations that allow it to be calculated have been developed and are used in engine simulations....

Knocking combustion research is crucially important because it determines engine durability, fuel consumption, and power density, as well as noise and emission performance. Current spark ignition (SI) engines suffer from both conventional knock and super-knock. Conventional knock limits raising the compression ratio to improve thermal efficiency du...

The production of increasingly efficient as well as clean engines has become imperative. Oxygenated fuels are often added to gasoline in order to achieve more efficient combustion. However, the effect on particulate emissions is not well understood. Chemical mechanisms are still uncertain for practical oxygenated fuels. In the present study, to avo...

This work presents experimental tests where lubricant oil was added to the engine in order to highlight its contribution to particle emissions from both gasoline and compressed natural gas spark-ignition engines. Three different ways of feeding the extra lubricant oil and two fuel-injection modes—port fuel injection and direct injection—were invest...

The purpose of this research was to analyze numerically the effect of adding nitrogen, hydrogen, reformer gas and hydrogen and nitrogen mixtures on the combustion and exhaust emissions properties of a natural gas-diesel dual-fuel reactivity controlled compression ignition (RCCI) engine at different engine loads. By using natural gas, emissions and...

One way to develop an understanding of soot formation and oxidation processes that occur during direct injection and combustion in an internal combustion engine is to image the natural luminosity from soot over time. Imaging is possible when there is optical access to the combustion chamber. After the images are acquired, the next challenge is to p...

Engine experiments were conducted on a heavy-duty single-cylinder engine to explore the effects of charge preparation, fuel stratification, and premixed fuel chemistry on the performance and emissions of Reactivity Controlled Compression Ignition (RCCI) combustion. The experiments were conducted at a fixed total fuel energy and engine speed, and ch...

In the current work, a series hybrid vehicle has been constructed that utilises a dual-fuel, reactivity controlled compression ignition (RCCI) engine. Full vehicle testing was conducted on chassis dynamometers over the US Environmental Protection Agency Federal Test Procedure, Highway Fuel Economy Test and US06 using RCCI combustion with commercial...

A combined reduced primary reference fuel (PRF)-alcohols (methanol/ethanol/propanols/butanols/n-pentanol) combustion kinetic mechanism composed of 161 species and 622 reactions was developed for engine combustion simulations. The obtained reduced PRF-alcohols mechanism was constructed with a hierarchical structure. Minor adjustments were performed...

Diesel engines have advantages due to their potential for high fuel conversion efficiency. However, it is necessary to reduce pollutant emissions, particularly NOx and soot to meet emission mandates. Many studies have shown that oxygenated fuel additives can effectively reduce soot emissions. In this research, to investigate the effect of oxygenate...

Reactivity controlled compression ignition (RCCI) combustion in a light-duty multicylinder engine (MCE) over transient operating conditions using fast response exhaust unburned hydrocarbon (UHC1), nitric oxide (NO), and particulate matter (PM) measurement instruments was investigated. RCCI has demonstrated improvements in efficiency along with low...

Low-temperature combustion offers an attractive combination of high thermal efficiency and low NOx and soot formation at moderate engine load. However, the kinetically-controlled nature of low-temperature combustion yields little authority over the rate of heat release, resulting in a tradeoff between load, noise, and thermal efficiency. While seve...

Computational fluid dynamics of gas-fueled large-bore spark ignition engines with pre-chamber ignition can speed up the design process of these engines provided that 1) the reliability of the results is not affected by poor meshing and 2) the time cost of the meshing process does not negatively compensate for the advantages of running a computer si...

A correlation was developed to predict the ignition delay of PRF blends at a wide range of engine-relevant operating conditions. Constant volume simulations were performed using Cantera coupled with a reduced reaction mechanism at a range of initial temperatures from 570-1860K, initial pressures from 10-100atm, oxygen mole percent from 12.6% to 21%...

The 4th Workshop of the Engine Combustion Network (ECN) was held September 5-6, 2015 in Kyoto, Japan. This manuscript presents a summary of the progress in experiments and modeling among ECN contributors leading to a better understanding of soot formation under the ECN “Spray A” configuration and some parametric variants. Relevant published and unp...

Low-temperature combustion (LTC) strategies have been an active area of research due to their ability to achieve high thermal efficiency while avoiding the formation of NOx and particulate matter. One of the largest challenges with LTC is the relative lack of authority over the heat release rate profile, which, depending on the particular injection...

A reduced chemical kinetic mechanism for tri-propylene glycol monomethyl ether has been developed and applied to computational fluid dynamics calculations for predicting combustion and soot formation processes. The reduced tri-propylene glycol monomethyl ether mechanism was combined with a reduced n-hexadecane mechanism and a poly-aromatic hydrocar...

Reactivity controlled compression ignition (RCCI) is an engine combustion strategy that utilizes in-cylinder fuel blending to produce low NOx and particulate matter (PM) emissions while maintaining high thermal efficiency. The current study investigates RCCI and conventional diesel combustion (CDC) operation in a light-duty multicylinder engine (MC...

To understand soot formation in a diesel engine fueled with different biodiesels, a numerical study was performed using the KIVA-3V code, combined with a multi-step phenomenological soot model. The simulations were used to predict differences in soot formation for three various biodiesel feedstock types. Good agreements on soot emissions were achie...

A reduced TRF-2,5-dimethylfuran (DMF25)-PAH combustion mechanism composed of 136 species and 617 reactions was developed for the engine combustion simulations. This mechanism was constructed based on a previous reduced TRF-PAH mechanism and a detailed DMF25 mechanism. First, the reduced DMF25 sub-mechanism was formulated using various mechanism red...

Premixed charge compression ignition (PCCI) combustion is capable of reducing nitrogen oxides (NOx) and soot emissions simultaneously, while remaining high fuel efficiency. Whereas, PCCI combustion still faces the challenges of the control of ignition timing and the expansion of operating range. In this study, by coupling a multi-dimensional comput...

Reactivity-controlled compression ignition is a low-temperature engine combustion strategy that utilizes in-cylinder blending of fuels with different autoignition characteristics to produce low NOx (oxides of nitrogen) and particulate matter emissions while maintaining high thermal efficiency. This study investigates reactivity-controlled compressi...

Reactivity Controlled Compression Ignition (RCCI) combustion in a light-duty multi-cylinder engine over transient operating conditions using fast response exhaust UHC1, NO and PM measurement instruments was investigated. RCCI has demonstrated improvements in efficiency along with low NOx and PM emissions by utilizing in-cylinder fuel blending, gene...

Reactivity Controlled Compression Ignition (RCCI) is an engine combustion strategy that utilizes in-cylinder fuel blending to produce low NOx and PM emissions while maintaining high thermal efficiency. The current study investigates RCCI and conventional diesel combustion (CDC) operation in a light-duty multi-cylinder engine using a transient capab...

In the present study a chamfered piston crown design was used in order to reduce unburned hydrocarbon (UHC) emissions from the ring-pack crevice. Compared to the conventional piston design, the chamfered piston showed 17%∼41% reduction in the crevice-borne UHC emissions in homogeneous charge compression ignition (HCCI) combustion. Through parametri...

A computationally efficient spray model is presented for the simulation of transient vaporizing engine sprays. It is applied to simulate high-pressure fuel injections in a constant volume chamber and in mixture preparation experiments in a light-duty internal combustion engine. The model is based on the Lagrangian-Particle/Eulerian-Fluid approach,...

Due to growing interest in utilizing natural gas as an alternative fuel in internal combustion engines, a study on the use of natural gas for dual-fuel combustion strategies in a heavy-duty engine was performed to examine the diesel pilot ignition (DPI) and reactivity controlled compression ignition (RCCI) combustion strategies. In Part 1 of this w...

Condensation of gaseous fuel is investigated in a low temperature combustion engine fueled with double directinjected diesel and premixed gasoline at two load conditions. Possible condensation is examined by considering real gas effects with the Peng-Robinson equation of state and assuming thermodynamic equilibrium of the two fuels. The simulations...

Advanced low temperature combustion (LTC) strategies are promising to achieve high efficiency and low emissions of nitric oxides (NOx) and Particulate Matter (soot). The thermal efficiency advantages are obtained through lower temperatures with reduced heat losses. A lower charge temperature and the sufficiently longer time available for mixing hel...

This paper is part of a larger body of experimental and computational work devoted to studying the role of close-coupled post injections on soot reduction in a heavy-duty optical engine. It is a continuation of an earlier computational paper. The goals of the current work are to develop new CFD analysis tools and methods and apply them to gain a mo...

Due to the new challenge of meeting number-based regulations for particulate matter (PM), a numerical and experimental study has been conducted to better understand particulate formation in engines fuelled with compressed natural gas. The study has been conducted on a Heavy-Duty, Euro VI, 4-cylinder, spark ignited engine, with multipoint sequential...

A spray–wall heat transfer model based on a newly published spray–wall interaction model was developed and implemented in the KIVA-3V engine computational fluid dynamics code to simulate the heat transfer related to wall films under spray impingement with application to direct-injection engines. The adopted spray–wall interaction model accounts for...

A diesel surrogate fuel model was developed by including n-decane, iso-octane, methylcyclohexane (MCH), and toluene, which represents the n-paraffins, iso-paraffins, cycloalkanes, and aromatic hydrocarbons in diesel fuel, respectively. The proportions of the components in the surrogate model were determined with special focus on reproducing the che...

Low-temperature combustion is an emerging engine technology that has the ability to yield low NOx and soot emissions while maintaining high fuel efficiency. Low-temperature combustion strategies include homogeneous charge compression ignition, premixed charge compression ignition, reactivity-controlled compression ignition and partially premixed co...

Reactivity controlled compression ignition (RCCI) has been shown to be capable of providing improved engine efficiencies coupled with the benefit of low emissions via in-cylinder fuel blending. Much of the previous body of work has studied the use of gasoline as the premixed low-reactivity fuel. However, there is interest in exploring the use of al...