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In this work, a dynamically loaded hydrodynamic journal bearing test rig is developed and introduced. The rig is a novel design, using a hydraulic actuator with fast acting spool valves to apply load to a connecting rod. This force is transmitted through the connecting rod to the large end bearing which is mounted on a spinning shaft. The hydraulic actuator allows for fully variable control and can be used to apply either static load in compression or tension, or dynamic loading to simulate engine operation. A variable speed electric motor controls shaft speed and is synchronized to the hydraulic actuator to accurately simulate loading to represent all four engine strokes. A high precision torque meter enables direct measurements of friction torque, while shaft position is measured via a high precision encoder.

Commercial vehicles are moving in the direction of improving brake thermal efficiency while also meeting future diesel emission requirements. This study is focused on improving efficiency by replacing the variable geometry turbine (VGT) turbocharger with a high-efficiency fixed geometry turbocharger. Engine-out (EO) NOX emissions are maintained by providing the required amount of exhaust gas recirculation (EGR) using a 48 V motor driven EGR pump downstream of the EGR cooler. This engine is also equipped with cylinder deactivation (CDA) hardware such that the engine can be optimized at low load operation using the combination of the high-efficiency turbocharger, EGR pump and CDA. The exhaust aftertreatment system has been shown to meet 2027 emissions using the baseline engine hardware as it includes a close coupled light-off SCR followed by a downstream SCR system.

Increasingly stringent emissions regulations require that modern diesel aftertreatment systems must warm up and begin controlling emissions shortly after startup. While several new aftertreatment technologies have been introduced that focus on lowering the aftertreatment activation temperature, the engine system still needs to provide thermal energy to the exhaust for cold start. A study was conducted to evaluate several engine technologies that focus on improving the thermal energy that the engine system provides to the aftertreatment system while minimizing the impact on fuel economy and emissions. Studies were conducted on a modern common rail 3L diesel engine with a custom dual loop EGR system. The engine was calibrated for low engine-out NOx using various combustion strategies depending on the speed/load operating condition.

The CO2 advantage coupled with the low NOX and PM potential of natural gas (NG) makes it well-suited for meeting future greenhouse gas (GHG) and NOX regulations for on-road medium and heavy-duty engines. However, because NG is mostly methane, reduced combustion efficiency associated with traditional NG fueling strategies can result in significant levels of methane emissions which offset the CO2 advantage due to reduced efficiency and the high global warming potential of methane. To address this issue, the unique co-direct injection capability of the Westport HPDI fuel system was leveraged to obtain a partially-premixed fuel charge by injecting NG during the compression stroke followed by diesel injection for ignition timing control. This combustion strategy, referred to as DI2, was found to improve thermal and combustion efficiencies over fumigated dual-fuel combustion modes.

The influence of nozzle geometry on spray and combustion of diesel continues to be a topic of great research interest. One area of promise, injector nozzles with micro-holes (i.e. down to 30 μm), still need further investigation. Reduction of nozzle orifice diameter and increased fuel injection pressure typically promotes air entrainment near-nozzle during start of injection. This leads to better premixing and consequently leaner combustion, hence lowering the formation of soot. Advances in numerical simulation have made it possible to study the effect of different nozzle diameters on the spray and combustion in great detail. In this study, a baseline model was developed for investigating the spray and combustion of diesel fuel at the Spray A condition (nozzle diameter of 90 μm) from the Engine Combustion Network (ECN) community.

As fuel economy becomes increasingly important in all markets, complete engine system optimization is required to meet future standards. In many applications, it is difficult to realize the optimum coolant or lubricant pump without first evaluating different sets of engine hardware and iterating on the flow and pressure requirements. For this study, a Heavy Duty Diesel (HDD) engine was run in a dynamometer test cell with full variability of the production coolant and lubricant pumps. Two test stands were developed to allow the engine coolant and lubricant pumps to be fully mapped during engine operation. The pumps were removed from the engine and powered by electric motors with inline torque meters. Each fluid circuit was instrumented with volume flow meters and pressure measurements at multiple locations. After development of the pump stands, research efforts were focused on hardware changes to reduce coolant and lubricant flow requirements of the HDD engine.

Heavy-duty (HD) internal combustion engines (ICE) have achieved quite high brake thermal efficiencies (BTE) in recent years. However, worldwide GHG regulations have increased the pace towards zero CO2 emissions. This, in conjunction with the ICE reaching near theoretical efficiencies means there is a fundamental lower limit to the GHG emissions from a conventional diesel engine. A large factor in achieving lower GHG emissions for a given BTE is the fuel, in particular its hydrogen to carbon ratio. Substituting a fuel like diesel with compressed natural gas (CNG) can provide up to 25% lower GHG at the same BTE with a sufficiently high substitution rate. However, any CNG slip through the combustion system is penalized heavily due to its large global warming potential compared to CO2. Therefore, new technologies are needed to reduce combustion losses in CNG-diesel dual fuel engines.

The engine power cylinder is comprised of the piston, piston rings, and cylinder. It accounts for a significant amount of total engine friction within reciprocating, internal combustion engines. Reducing power cylinder friction is key to the development of efficient internal combustion engines. However, isolating individual power cylinder tribocouples for detailed analysis can be challenging. In this work, a new reciprocating liner test rig is developed and introduced. The rig design is novel, using a stationary piston and a reciprocating cylinder liner. Friction is calculated from the force measured in the connecting rod which supports the piston. The rig allows for independent control of peak cylinder pressure, speed, and lubricant temperature. Using the newly developed test rig, several technologies for friction reduction are evaluated and compared.

Increased electrification of future heavy-duty engines and vehicles can enable many new technologies to improve efficiency. Electrified oil pumps are one such technology that provides the ability to reduce or turn off the piston oil cooling jets and simultaneously reduce the oil pump flow to account for the reduced flow rate required. This can reduce parasitic losses and improve overall engine efficiency. In order to study the potential impact of reduced oil cooling, a GT-Power engine model prediction of piston temperature was calibrated based on measured piston temperatures from a wireless telemetry system. A simulation was run in which the piston oil cooling was controlled to target a safe piston surface temperature and the resulting reduction in oil cooling was determined. With reduced oil cooling, engine BSFC improved by 0.2-0.8% compared to the baseline with full oil cooling, due to reduced heat transfer from the elevated piston temperatures.

Numerous studies have characterized the impact of high injection pressure and small nozzle holes on spray quality and the subsequent impact on combustion. Higher injection pressure or smaller nozzle diameter usually reduce soot emissions owing to better atomization quality and fuel-air mixing enhancement. The influence of nozzle geometry on spray and combustion of diesel continues to be a topic of great research interest. An alternate approach impacting spray quality is investigated in this paper, specifically the impact of non-circular nozzles. The concept was explored experimentally in an optically accessible constant-volume combustion chamber (CVCC). Non-reacting spray evaluations were conducted at various ambient densities (14.8, 22.8, 30 kg/m3) under inert gas of Nitrogen (N2) while injection pressure was kept at 100 MPa. Shadowgraph imaging was used to obtain macroscopic spray characteristics such as spray structure, spray penetration, and the spray cone angle.

Fluid-Structure Interaction (FSI) simulation approach can be used to simulate a turbocharger. However, this predictive 3D simulation encounters the challenge of a long computational time. The impeller speed can be above 100,000 rpm, and generally a CFD solver limits the maximum movement of the impeller surface per time step. The maximum movement must be a fraction (~0.3) of the cell length, thus the time step will be very small. A Multiple Reference Frame (MRF) approach can reduce computational time by eliminating the need to regenerate the mesh at each time-step to accommodate the moving geometry. A static local reference zone encompassing the impeller is created and the impact of the impeller movement is modeled via a momentum source. However, the MRF approach is not a predictive simulation because the impeller speed must be given by the User. A new simulation approach was introduced that coupled the FSI and MRF approach.

In this work, a novel bearing test rig was used to evaluate the impact of oil viscoelasticity on friction torque and oil film thickness in a hydrodynamic journal bearing. The test rig used an electric motor to rotate a test journal, while a hydraulic actuator applied radial load to the connecting rod bearing. Lubrication of the journal bearing was accomplished via a series of axial and radial drillings in the test shaft and journal, replicating oil delivery in a conventional engine crankshaft. Journal bearing inserts from a commercial, medium duty diesel engine (Cummins ISB) were used. Oil film thickness was measured using high precision eddy current sensors. Oil film thickness measurements were taken at two locations, allowing for calculation of minimum oil film thickness. A high-precision, in-line torque meter was used to measure friction torque. Four test oils were prepared and evaluated.

With increasing diesel engine emissions regulations and the desire to increase overall thermal efficiency of the engine, various combustion concepts have been explored. One of the potential pathways to higher efficiency is through reduction of in-cylinder heat transfer. In this paper, a concept aimed at decreasing in-cylinder heat transfer through increased piston temperature is explored. In order to increase piston temperature and ideally reduce in-cylinder heat transfer, a Zero-Oil-Cooling (ZOC) piston concept was explored. To study this concept, the test engine was modified to allow piston oil cooling to be deactivated so that its impact on parameters such as BTE, piston temperature, and emissions could be evaluated. The engine was equipped with in-cylinder pressure measurement for combustion analysis as well as a piston temperature telemetry system to evaluate piston crown temperature. This paper will discuss the process by which the engine was modified to achieve ZOC and tested.