<p>  </p> <p>A Cummins 6.7L natural gas engine enabled with VVA was installed in a research test cell at Purdue’s Ray Herrick Laboratories for experimental testing. The stock engine which was connected to an AC dynameter was mounted on a movable test bed outfitted with numerous sensors, a charge air cooler, and an external heat exchanger. In the engine control room, a few different systems were set up to run the dyno, collect data from the engine sensors, and monitor the safety apparatuses in the test cell. </p> <p>After the test cell setup was completed, an initial baseline testing was performed to compare the stock engine operation with the baseline engine data given in the Cummins fuel map. The testing was used to verify the engines stock functionality and troubleshoot some additional issues before setting the boundary conditions. Once the boundary conditions were set, a final stock engine testing was performed at rated to check for repeatability and verify stock engine operation following the engine modifications made to accommodate the VVA. </p> <p>Following the baseline testing, the VVA system was assembled on the standalone rig to verify its operation before mounting it on the engine. In order to run the natural gas valve profiles received from Cummins, the VVA controller gains were retuned and the LVDT sensors were calibrated so that the desired closing, opening and lift behaviors were achieved. After verifying the VVA’s functionality, the hardware was mounted on the engine for the VVA experimental testing. </p> <p>The initial VVA testing was focused on understanding the impacts of intake valve modulation on the gas exchange process. Based on previous simulation work, reductions in pumping work leading to better fuel economy is one expected outcome. Experimental testing data related to the engine performance and operation was used to compare each IVC case to the stock IVC timing. These results were also compared to the previous GT-Power work to identify any apparent trends.</p> <p>Future work includes using VVA to further improve efficiency in the part load region, and reduce knock at higher loads. Additionally, the incorporation of a laser based in-cylinder sensing system will help to optimize the capability of VVA.</p>

Today, the investigation of fuel economy improvements in internal combustion engines (ICEs) has become the most significant research interest among the automobile manufacturers and researchers. The scarcity of natural resources, progressively increasing oil prices, carbon dioxide taxation and stringent emission regulations all make fuel economy research relevant and compelling. The enhancement of engine performance solely using incylinder techniques is proving increasingly difficult and as a consequence the concept of exhaust energy recovery has emerged as an area of considerable interest. Three main energy recovery systems have been identified that are at various stages of investigation. Vapour power bottoming cycles and turbo-compounding devices have already been applied in commercially available marine engines and automobiles. Although the fuel economy benefits are substantial, system design implications have limited their adaptation due to the additional components and the complexity of the resulting system. In this context, thermo-electric (TE) generation systems, though still in their infancy for vehicle applications have been identified as attractive, promising and solid state candidates of low complexity. The performance of these devices is limited to the relative infancy of materials investigations and module architectures. There is great potential to be explored. The initial modelling work reported in this study shows that with current materials and construction technology, thermo-electric devices could be produced to displace the alternator of the light duty vehicles, providing the fuel economy benefits of 3.9%-4.7% for passenger cars and 7.4% for passenger buses. More efficient thermo-electric materials could increase the fuel economy significantly resulting in a substantially improved business case. The dynamic behaviour of the thermo-electric generator (TEG) applied in both, main exhaust gas stream and exhaust gas recirculation (EGR) path of light duty and heavy duty engines were studied through a series of experimental and modelling programs. The analyses of the thermo-electric generation systems have highlighted the need for advanced heat exchanger design as well as the improved materials to enhance the performance of these systems. These research requirements led to the need for a systems evaluation technique typified by hardware-in-the-loop (HIL) testing method to evaluate heat exchange and materials options. HIL methods have been used during this study to estimate both the output power and the exhaust back pressure created by the device. The work has established the feasibility of a new approach to heat exchange devices for thermo-electric systems. Based on design projections and the predicted performance of new materials, the potential to match the performance of established heat recovery methods has been demonstrated.

<div> In recent decades as environmental concerns and the cost and availability of fossil fuels have become more pressing issues, the need to extract more work from each drop of fuel has increased accordingly. Electrification has been identified as a way to address these issues in vehicles powered by internal combustion engines, as it allows existing engines to be operated more efficiently, reducing overall fuel consumption. Two applications of electrification are discussed in the work presented: a series-electric hybrid powertrain from an on-road class 8 truck, and an electrically supercharged diesel engine for use in the series hybrid power system of a wheel loader.</div><div> </div><div> The first application is an experimental powertrain developed by a small start-up company for use in highway trucks. The work presented in this thesis shows test results from routes along (1) Interstate 75 between Florence, KY, and Lexington, KY, and (2) Interstates 74 and 70 east of Indianapolis, during which tests the startup collected power flow data from the vehicle's motor, generator, and battery, and three-dimensional position data from a GPS system. Based on these data, it was determined that the engine-driven generator provided an average of 15% more propulsive energy than required due to electrical losses in the drivetrain. Some of these losses occured in the power electronics, which are shown to be 82% - 92% efficient depending on power flow direction, but the battery showed significant signs of wear, accounting for the remainder of these electrical losses. Overall, most of the system's fuel savings came from its regenerative braking capability, which recaptured between 3% and 12% of the total drive energy output. Routes with significant grade changes maximize this energy recapture percentage, but it is shown minimizing drag and rolling resistance with a more modern truck and trailer could further increase this energy capture to between 8% and 18%.</div><div> </div><div> In the second application, an electrified air handling system is added to a 4.5L engine, allowing it to replace the 6.8L engine in John Deere's 644K hybrid wheel loader. Most of the fuel savings arise from downsizing the engine, so in this case an electrically driven supercharger (eBooster) allows the engine to meet the peak torque requirements of the larger, original engine. In this thesis, a control-oriented nonlinear state space model of the modified 4.5L engine is presented and linearized for use in designing a robust, multi-input multi-output (MIMO) controller which commands the engine's fueling rate, eBooster, eBooster bypass valve, exhaust gas recirculation (EGR) valve, and exhaust throttle. This integrated control strategy will ultimately allow superior tracking of engine speed, EGR fraction, and air-fuel ratio (AFR) targets, but these performance gains over independent single-input single-output control loops for each component demand linear models that accurately represent the engine's gas exchange dynamics. To address this, a physics-based model is presented and linearized to simulate pressures, temperatures, and shaft speeds based on sub-models for exhaust temperature, cylinder charge flow, valve flow, compressor flow, turbine flow, compressor power, and turbine power. The nonlinear model matches the truth reference engine model over the 1200 rpm - 2000 rpm and 100 Nm - 500 Nm speed and torque envelope of interest within 10% in steady state and 20% in transient conditions. Two linear models represent the full engine's dynamics over this speed and torque range, and these models match the truth reference model within 20% in the middle of the operating envelope. However, specifically at (1) low load for any speed and (2) high load at high speed, the linear models diverge from the nonlinear and truth reference models due to nonlinear engine dynamics lost in linearization. Nevertheless, these discrepancies at the edges of the engine's operating envelope are acceptable for control design, and if greater accuracy is needed, additional linear models can be generated to capture the engine's dynamics in this region.</div>

The urgent need to reduce green house gas emissions from the transport sector, particularly from heavy-duty trucks, has underscored the importance of developing more efficient internal combustion engines. Using computational fluid dynamics (CFD), this work investigated the impact of valve seat geometry on in-cylinder swirl, addressing a gap in research. Additionally, the suitability of steady-state simulations for providing valid qualitative data on port flow was assessed. To answer both research questions, two approaches were followed: steady-state port flow RANS simulations, and transient RANS simulations in a running engine setup. The results from the steady-state simulations highlighted the limitations of this approach to qualitatively predict swirl, as this quantity is highly dependent on the mesh. Despite these limitations, the steady-state simulations were still able to capture the trade-off between swirl and discharge coefficient, outlined in the literature. Transient simulations revealed that in-cylinder swirl is affected by the geometry of the valve seats. It was found that valve seats that direct the flow towards the liner, while avoiding strong flow separation tend to promote higher swirl, whereas valve seats that induce strong flow separation lead to lower swirl ratios. Despite the trade-off between swirl and volumetric efficiency, the volumetric efficiency losses were found to be practically negligible. The study emphasizes the need for a more comprehensive set of simulations, including more valve lifts and pressure ratios. Given the unsuitability of the steady-state simulations to predict swirl trends, future investigations should focus on replacing this approach by transient simulations with steady-state geometry and boundary conditions, properly addressing flow time-dependency at relatively low computational cost, and facilitating validation with experimental data.

<div>A growing global population and improved standard of living in developing countries have resulted in an unprecedented increase in energy demand over the past several decades. While renewable energy sources are increasing, a huge portion of energy is still converted into useful work using heat engines. The combustion process in diesel and petrol engines releases carbon dioxide and other greenhouse gases as an unwanted side-effect of the energy conversion process. By improving the efficiency of internal combustion engines, more chemical energy stored in petroleum resources can be realized as useful work and, therefore, reduce global emissions of greenhouse gases. This research focused on improving the thermal efficiency of opposed-piston engines, which, unlike traditional reciprocating engines, do not use a cylinder head. The cylinder head is a major source of heat loss in reciprocating engines. Therefore, the opposed-piston engine has the potential to improve overall engine efficiency relative to inline or V-configuration engines.</div><div><br></div>The objective of this research project was to further improve the design of opposed-piston engines by using computational fluid dynamics (CFD) modeling to optimize the engine geometry. The CFD method investigated the effect of intake port geometry and exhaust piston lead angle on the scavenging process and in-cylinder turbulence. After the CFD data was analyzed, scavenging efficiency was found insensitive to transfer port geometry and exhaust piston lead angle with a maximum change of 0.61%. Trapping efficiency was altered exclusively by exhaust piston lead angle and changed from 18% to 26% as the lead angle was increased. The in-cylinder turbulence parameters of the engine (normalized swirl circulation, normalized tumble circulation, and normalized TKE) experienced more complex relationships. All turbulence parameters were sensitive to changing transfer port geometry and exhaust piston lead angle. Some examples of trends seen during the analysis include: an increase in normalized swirl circulation from 0.01 to 4.45 due to changes in swirl angle, a change in normalized tumble circulation from -28.52 to 21.11 as swirl angle increased, and an increase in normalized tumble circulation from 14.20 to 33.68 as exhaust piston lead angle was increased. Based on the present work, an optimum configuration was identified for a swirl angle of 15°, a tilt angle of 10°, and an exhaust piston lead angle of 20°. Future work includes expanding the numerical model’s domain to support a complete cylinder-port configuration, adding combustion products to the diffusivity equation in the UDF, and running additional test cases to describe the entire input space for the sensitivity analysis.<br>