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An experimental piston compounded engine was designed with guidance from thermodynamic modeling, then was built and tested to compare the model predictions to measured results. The piston-compounded concept has shown great potential for improvements in efficiency over current state-of-the-art light-duty engines through the use of an efficient second expansion process to more fully recover energy still present in the exhaust gasses, and was further developed into the Downsized Boosted Dilute Combustion, Exhaust Compounded (DBDC+EC) engine presented here. This paper documents some of the more unique design elements of this engine as well as a performance comparison between test data and modeling expectations. Ultimately, an experimental stoichiometric spark-ignited piston compounded engine was designed, five blocks were built, and collectively they were run for thousands of hours.

An experimental piston compounded engine was designed with guidance from thermodynamic modeling, then was built and tested to compare the model predictions to measured results. This Downsized Boosted Dilute Combustion, Exhaust Compounded (DBDC+EC) engine concept has shown great potential for improvements in efficiency at high loads through extended second expansion process, but suffered from excessive expander cylinder pumping and low exhaust temperatures at low loads. Four expander operating strategies were experimentally tested and simulated at a range of engine speeds and loads to determine the most efficient method to deactivate the piston compounding at low loads. The most effective method involved deactivating all the expander valves and operating it as an air-spring while diverting power cylinder exhaust gasses through a separate bypass port.

Particulate filters (PF) are a highly effective after-treatment device that reduces particulate matter emissions, a rising environmental concern in the automotive industry. However, accumulation of solid particles during the PF filtration process increases engine backpressure considerably, which can have a negative impact on engine efficiency, acoustics, and gaseous emissions. In this area, an accurate pressure drop model helps to better understand the effect of accumulated solid particles in the PF on engine backpressure, aiding in design and regeneration considerations without physical testing. These effects are further improved on board the vehicle using a single equation pressure drop model with a relatively low computational cost. This article presents a thorough history of PF pressure drop models and their advancements.

Diesel knock and ringing combustion in compression ignition (CI) engines are largely an unavoidable phenomenon and are partially related to the overall effectiveness of the fuel injection process. Modern electronic fuel injection systems have been effective at reducing the intensity of knock in CI engines, largely through optimization of fuel injection timing, as well as higher operating pressures that promote enhanced fuel and air mixing. In this effort, a single-cylinder CI engine was tested under a number of different combustion strategies, including a comparison of mechanical and electronic injection systems, increasing fuel injection pressures for biodiesel fuels, and the usage of dual-fuel combustion with compressed natural gas (CNG). Using in-cylinder pressure traces and engine operational data, the difference in injection mechanisms, fuel preparation, and their effects on knock intensity is clearly illustrated.

Utilizing a higher compression ratio in a Compression Ignition (CI) engine grants an obvious advantage of improved thermal efficiency. However, the resulting combustion temperatures promote dissociation ensuing in increased nitrogen oxide (NOx) emissions. Unfortunately, due to the inherent properties of CI combustion, it is difficult to achieve simultaneous reduction of NOx and particulate matter (PM) through conventional combustion methods. Taking a different route though accomplishing Homogeneous Charge Compression Ignition (HCCI) in CI engines will largely eliminate NOx and PM; however, combustion can result in a significant increase in hydrocarbon (HC) and carbon monoxide (CO) emissions due to the low volatility of diesel fuel. Hence, this work attempts another avenue of Low Temperature Combustion (LTC) by employing Pre-mixed Charge Compression Ignition (PCI) combustion on a comparatively higher compression ratio (21.2) single cylinder CI engine.

The recent increase in natural gas availability has made compressed natural gas (CNG) an option for fueling the transportation sector of the United States economy. In particular, CNG is advantageous in dual-fuel operation alongside ultra low sulfur diesel (ULSD) for compression ignition (CI) engines. This work investigates the usage of natural gas mixtures at varying Energy Substitution Rates (ESRs) within a high compression ratio single-cylinder CI engine, including performance and heat release modeling of dual-fuel combustion. Results demonstrate the differing behavior of utilizing CNG at various substitution rates.

As climate change drives the exploration into new and alternative fuels, biodiesel has emerged as a promising alternative to traditional diesel fuel. To further increase the viability of biodiesel, a unique system at the University of Kansas utilizes glycerin, the primary byproduct of biodiesel production, for power generation. This system converts glycerin into a hydrogen-rich gas (syngas) that is sent to an engine-generator system in one continuous flow process. The current setup allows for running the engine-generator system on pure propane, reformed propane, or reformed glycerin, with each fuel serving a unique purpose. This paper discusses upgrades in pure propane operation that serves the intent of preheating the engine prior to syngas operation and establishing the baseline energy requirement for fueling the system.

Given the need of the automotive industry to improve fuel efficiency, many companies are moving towards lean burn and low temperature combustion regimes. Critical control of these methods requires an accurate Exhaust Gas Recirculation (EGR) system that can maintain its desired rate and temperature. In this area, the literature illustrates different methodologies to control and monitor this EGR system; however, it lacks a discussion of how the non-linear nature of wave dynamics and time responses of an engine must be taken into account. In order to perform research into the use of EGR for these combustion regimes, an automated, closed-loop EGR system that uses a microprocessor to compute the slope change of the EGR rate and temperature as part of its feedback algorithm was constructed for use in a teaching and research laboratory. The findings illustrate that the system works as intended by replicating known combustion trends with EGR.

In-cylinder engine modeling is a necessary aspect of combustion research. In particular, simulating heat release connects variable combustion behavior to fuel properties through the 1st Law of Thermodynamics. One extension of such models is to evaluate changes to in-cylinder behavior using the Second Law of Thermodynamics in order to identify the peak period of availability for work extraction. Thus, Second Law models are a useful tool to augment research into alternative fuel usage and optimization. These models also help identify internal irreversibilities that are separate from heat transfer and exhaust gas losses. This study utilizes a multi-zone 1st and 2nd Law Heat Release model to characterize the changes in combustion behavior of a number of neat fuels used in a single-cylinder compression ignition (CI) engine.

Biodiesel is a potential alternative to Ultra Low Sulfur Diesel (ULSD); however, it often suffers from increased fuel consumption in comparison to ULSD when injection timings and/or pressures are similar. To decrease fuel consumption, increasing biodiesel injection pressure has been found to mitigate the issues associated with its relatively high viscosity and lower energy content. When doing so, the literature indicates decreased emissions, albeit with potentially greater nitrogen oxide (NOx) emissions in contrast to ULSD. In order to better understand the trade-off between fuel consumption and NOx emissions, this study explores the influence of fuel injection pressure on ULSD, Waste Cooking Oil (WCO) biodiesel, and their blends in a single-cylinder compression ignition (CI) engine. In particular, fuel injection pressures and timings for WCO biodiesel and blended fuels are adjusted to attempt to mimic the in-cylinder pressure profile of operation using ULSD.

The use of Compressed Natural Gas (CNG) has demonstrated the potential to decrease Particulate Matter (PM) and nitrogen oxide (NOx) emissions simultaneously when used in a dual-fuel application with diesel fuel functioning as the ignition source. However, some authors do find that NOx emissions can increase. One postulation is that the conflicting results in the literature may be due to the difference in composition of natural gas around the world. Therefore, in order to investigate if CNG composition influences combustion performance and emissions, four unique mixtures of CNG were tested (i.e., 87% to 96% methane) while minimizing the combined difference of the density, heating value, and constant pressure specific heat of each mixture. This was accomplished at moderate energy substitution ratios (up to 40%) in a single cylinder engine operating at various loads.

The growth of hydraulic fracking has resulted in a dramatic cost reduction of Compressed Natural Gas (CNG), a low carbon fuel. CNG cannot be used as singular fuel in conventional Compression Ignition (CI) engines because of its high auto-ignition characteristics. However, CNG-assisted diesel combustion represents a means to shift the energy consumption of CI engines away from liquid fossil fuels. Calculation of the rate of heat release is vital for understanding and optimizing this mode of engine operation. A previously constructed three-zone equilibrium heat release model that is calibrated to engine exhaust emission measurements was augmented in order to allow for the addition of CNG in the engine intake. The model was also adapted to permit reuse of unburned CNG gas with other exhaust species via exhaust gas recirculation. This is because experiments demonstrated a potentially significant increase in methane emissions under high CNG flowrates.

Recently, ozone addition has come under scrutiny as a means of controlling ignition timing for Low Temperature (LTC) combustion, which defeats the NOx-PM tradeoff using a highly dilute, homogeneous mixture. This is because ozone decomposes into atomic oxygen and hydroxyl radicals that influence the early phases of the ignition delay process. In order to understand ozone's influence on combustion better, this work analyzes the effects of ozone-assisted combustion for a single-cylinder, direct-injection Compression Ignition engine via a mechanical pump-line-nozzle fuel system and an electronically controlled common-rail fuel injection system. Experimental outcomes indicate a relatively small influence of ozone for the mechanical injection system with a comparably decreased effect for the common rail system.

Diesel Particulate Filters (DPFs) have become a required aftertreatment device for Compression Ignition engine exhaust cleanup of Particulate Matter (PM). Moreover, with the increased prevalence of Spark Ignition Direct Injection (SIDI) systems, discussions are currently underway regarding the need of Gasoline Particulate Filters to handle the PM emanating from their combustion process. In this area, the two-channel DPF model has been widely successful in predicting the temperature, pressure drop, and species conversion in these devices. Because of the need to simulate compressible flow through the channels and a porous wall, these models have a difficult time achieving real-time predictive results suitable for an Engine Control Unit (ECU). As a result, this effort describes the creation of a lumped DPF model intended for an ECU. Model formulation was based on the standard governing equations, but simplified in order to remove as much computational overhead as possible.

Significant progress towards reducing diesel engine fuel consumption and emissions is possible through the simultaneous Waste Heat Recovery (WHR) and Particulate Matter (PM) filtration in a novel device described here as a Diesel Particulate Filter Heat Exchanger (DPFHX). This original device concept is based on the shell-and-tube heat exchanger geometry, where enlarged tubes contain DPF cores, allowing waste heat recovery from engine exhaust and allowing further energy capture from the exothermic PM regeneration event. The heat transferred to the working fluid on the shell side of the DPFHX becomes available for use in a secondary power cycle, which is an increasingly attractive method of boosting powertrain efficiency due to fuel savings of around 10 to 15%. Moreover, these fuel savings are proportional to the associated emissions reduction after a short warm-up period, with startup emissions relatively unchanged when implementing a WHR system.

In order to perform cutting-edge engine research that applies to modern Compression Ignition (CI) engines, a sophisticated test cell is needed that allows control of the engine and its auxiliary systems. The primary obstacle to the completion of such a test cell is the up-front expense. This paper covers the construction of a low cost, single-cylinder engine test cell while demonstrating the type of research that can be accomplished along the way. The components necessary for the construction, instrumentation, and operation of such a test cell, neglecting emissions analysis equipment, can be obtained for less than $150,000. The engine utilized, a naturally-aspirated single-cylinder Yanmar L100V, was purchased as an engine-generator package.

A timing sweep to correlate the location of Maximum Brake Torque (MBT) was completed on a single-cylinder, direct injected compression ignition engine that was recently upgraded to a high-pressure rail injection system for better engine control. This sweep included emissions monitoring for carbon dioxide, carbon monoxide, particulate matter, hydrocarbons, and oxides of nitrogen for the calibration of a heat release model, as well as the opportunity to relate MBT timing to brake-specific emissions production. The result of this timing sweep was a relatively linear correlation between injection delay and peak pressure timing. In addition, a number of other MBT timing methodologies were tested indicating their applicability for immediate feedback upon engine testing, particularly mass fraction burned correlations. Emissions were either strongly correlated to MBT timing (with emissions being minimized in the vicinity of MBT), or were completely independent of MBT.

Refinements were made to a post-processing technique, termed the Thermal Stratification Analysis (TSA), that couples the mass fraction burned data to ignition timing predictions from the autoignition integral to calculate an apparent temperature distribution from an experimental HCCI data point. Specifically, the analysis is expanded to include all of the mass in the cylinder by fitting the unburned mass with an exponential function, characteristic of the wall-affected region. The analysis-derived temperature distributions are then validated in two ways. First, the output data from CFD simulations are processed with the Thermal Stratification Analysis and the calculated temperature distributions are compared to the known CFD distributions.

Engine manufacturers are considering the implementation of thermodynamic cycles for Waste Heat Recovery (WHR) in order to increase Internal Combustion Engine (ICE) system thermal efficiency. For these secondary cycles, the literature illustrates the preference of Organic Rankine Cycles (ORC's) due to its simplicity and efficient recovery of the medium grade waste heat found in engine exhaust. This paper simulates the heat recovery capacity of eight dry fluids (butane, pentane, hexane, cyclopentane, benzene, toluene, R245fa, and R123) for an ORC based on the exhaust from a single-cylinder diesel engine-generator operating under five different loading conditions. The model, developed using REFPROP and the Matlab Optimization Toolbox, represents the physical components using isentropic pump and expander efficiencies, along with two-zone heat exchangers. All fluids present cycle efficiencies between 10-15%, with the heaviest hydrocarbons generating the largest amount of work.

Selective Catalytic Reduction (SCR) catalysts used in Lean NOx Trap (LNT) - SCR exhaust aftertreatment systems typically encounter alternating oxidizing and reducing environments. Reducing conditions occur when diesel fuel is injected upstream of a reformer catalyst, generating high concentrations of hydrogen (H₂), carbon monoxide (CO), and hydrocarbons to deNOx the LNT. In this study, the functionality of an iron (Fe) zeolite SCR catalyst is explored with a bench top reactor during steady-state and cyclic transient SCR operation. Experiments to characterize the effect of an LNT deNOx event on SCR operation show that adding H₂ or CO only slightly changes SCR behavior with the primary contribution being an enhancement of nitrogen dioxide (NO₂) decomposition into nitric oxide (NO). Exposure of the catalyst to C₃H₆ (a surrogate for an actual exhaust HC mixture) leads to a significant decrease in NOx reduction capabilities of the catalyst.