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As emerging automated vehicle technology is making advances in safety and reliability, engineers are also exploring improvements in energy efficiency with this new paradigm. Powertrain efficiency receives due attention, but also impactful is finding ways to reduce driving losses in coordinated-driving scenarios. Efforts focused on simulation to quantify road load improvements require a sufficient amount of background validation work to support them. This study uses a practical approach to directly quantify road load changes by testing the coordinated driving of two vehicles on a test track at various speeds (64, 88, 113 km/h) and vehicle time gaps (0.3 to 1.3 s). Axle torque sensors were used to directly measure the load required to maintain steady-state speeds while following a lead vehicle at various gap distances.

It is widely understood that cold ambient temperatures negatively impact vehicle system efficiency. This is due to a combination of factors: increased friction (engine oil, transmission, and driveline viscous effects), cold start enrichment, heat transfer, and air density variations. Although the science of quantifying steady-state vehicle component efficiency is mature, transient component efficiencies over dynamic ambient real-world conditions is less understood and quantified. This work characterizes wheel assembly efficiencies of a conventional and electric vehicle over a wide range of ambient conditions. For this work, the wheel assembly is defined as the tire side axle spline, spline housing, bearings, brakes, and tires. Dynamometer testing over hot and cold ambient temperatures was conducted with a conventional and electric vehicle instrumented to determine the output energy losses of the wheel assembly in proportion to the input energy of the half-shafts.

Two modern light-duty passenger vehicles were selected for chassis dynamometer testing to evaluate differences in performance end efficiency resulting from CNG and gasoline combustion in a vehicle-based context. The vehicles were chosen to be as similar as possible apart from fuel type, sharing similar test weights and identical driveline configurations. Both vehicles were tested over several chassis dynamometer driving cycles, where it was found that the CNG vehicle exhibited 3-9% lower fuel economy than the gasoline-fueled subject. Performance tests were also conducted, where the CNG vehicle's lower tractive effort capability and longer acceleration times were consistent with the lower rated torque and power of its engine as compared to the gasoline model. The vehicles were also tested using quasi-steady-state chassis dynamometer techniques, wherein a series of engine operating points were studied.

The first commercially available Plug-In Hybrid Electric Vehicle (PHEV), the General Motors (GM) Volt, was introduced into the market in December 2010. The Volt's powertrain architecture provides four modes of operation, including two that are unique and maximize the Volt's efficiency and performance. The electric transaxle has been specially designed to enable patented operating modes both to improve the electric driving range when operating as a battery electric vehicle and to reduce fuel consumption when extending the range by operating with an internal combustion engine (ICE). However, details on the vehicle control strategy are not widely available because the supervisory control algorithm is proprietary. Since it is not possible to analyze the control without vehicle test data obtained from a well-designed Design-of-Experiment (DoE), a highly instrumented GM Volt, including thermal sensors, was tested at Argonne National Laboratory's Advanced Powertrain Research Facility (APRF).

As new advanced-technology vehicles are becoming more mainstream, analysts are studying their potential impact on petroleum use, carbon emissions, and smog emissions. Determining the potential impacts of widespread adoption requires testing and careful analysis. PHEVs possess unique operational characteristics that require evaluation in terms of actual in-use driving habits. SAE J2841, “Utility Factor Definitions for Plug-In Hybrid Electric Vehicles Using 2001 U.S. DOT National Household Travel Survey Data,” published by SAE in 2009 with a revision in 2010, is a guide to using DOT's National Household Travel Survey (NHTS) data to estimate the relative split between driving in charge-depleting (CD) mode and charge-sustaining (CS) mode for a particular PHEV with a given CD range. Without this method, direct comparisons of the merits of various vehicle designs (e.g., efficiency and battery size) cannot be made among PHEVs, or between PHEVs and other technologies.

Testing vehicles for emissions and fuel economy has traditionally been conducted with a single-axle chassis dynamometer. The 2006 SAE All Wheel Drive Symposium cited four wheel drive (4WD) and all wheel drive (AWD) sales as climbing from 20% toward 30% of a motor vehicle market share. With an increasing number of four wheel-drive vehicles being introduced to the market place, certification testing for emissions and fuel economy has been changed to allow both two wheel drive and four wheel drive testing [1]. As manufacturers plan to test these vehicles in this mode, test methods need to be developed to allow for these changes. This paper focuses on the tie down methods available for 4WD testing to determine possible effects of test methodologies on a traditional 4WD Vehicle and a hybrid vehicle.

An electronic particulate matter sensor (EPMS) developed at the University of Texas was used to characterize exhaust gases from a single-cylinder diesel engine and a light-duty diesel vehicle. Measurements were made during transient tip-in events with multiple sensor configurations in the single-cylinder engine. The sensor was operated in two modes: one with the electric field energized, and the other with no electric field present. In each mode, different characteristic signals were produced in response to a tip-in event, highlighting the two primary mechanisms of sensor operation. The sensor responded to both the natural charge of the particulate matter (PM) emitted from the engine, and was also found to create a signal by charging neutral particles. The characteristics of the two mechanisms of operation are discussed as well as their implications on the placement and operation of the sensor.

This paper presents the latest developments in the design and performance of an electronic particulate matter (PM) sensor developed at The University of Texas at Austin (UT) and suitable, with further development, for applications in active engine control of PM emissions. The sensor detects the carbonaceous mass component of PM in the exhaust and has a time-resolution less than 20 (ms), allowing PM levels to be quantified for engine transients. Sample measurements made with the sensor in the exhaust of a single-cylinder light duty diesel engine are presented for both steady-state and transient operations: a steady-state correlation with gravimetric filter measurements is presented, and the sensor response to rapid increases in PM emission during engine transients is shown for several different tip-in (momentary increases in fuel delivery) conditions.

It is a very challenging problem to reliably ignite extremely lean mixtures, especially for the low speed, high load conditions of large-bore natural gas engines. If these engines are to be use for the distributed power generation market, it will require operation with higher boost pressures and even leaner mixtures. Both place greater demands on the ignition system. The railplug is a very promising ignition system for lean burn natural gas engines with its high-energy deposition and high velocity plasma arc. It requires care to properly design railplugs for this new application, however. For these engines, in-cylinder pressure and mixture temperature are very high at the time of ignition due to the high boost pressure. Hot spots may exist on the electrodes of the ignitor, causing pre-ignition problems. A heat transfer model is proposed in this paper to aid the railplug design. The electrode temperature was measured in an operating natural gas engine.

Ignition of extremely lean or dilute mixtures is a very challenging problem. Therefore, it is essential for the engine development engineer to understand the fundamentals and limitations of existing ignition systems. This paper presents a new railplug ignition concept, a high-energy ignition system, which can enhance ignition of very lean mixtures by means of its high-energy deposition and high velocity jet of the plasma. This paper presents initial results of tests using an inductive ignition system, a capacitor discharge ignition system, and a railplug high-energy ignition system. Discharge characteristics, such as time-resolved voltage, current, and luminous emission were measured. Spark plug and railplug ignition are compared for their effects on combustion stability of a natural gas engine. The results show that railplugs have a very strong arc-phase that can ensure the ignition of very dilute mixtures.

In order to determine the factors that affect fuel economy quantitatively, the power flows through the major powertrain components were measured during operation over transient cycles. The fuel consumption rate and torque and speed of the engine output and axle shafts were measured to assess the power flows in a vehicle with a CVT. The measured power flows were converted to energy loss for each component to get the efficiency. Tests were done at Phase 1 and Phase 3 of the FTP and for two different CVT shift modes. The measured energy distributions were compared with those from the ADVISOR simulation and to results from the PNGV study. For both the Hot 505 and the Cold 505, and for both shift modes, the major powertrain loss occurs in the engine, including or excluding standby losses. However, the efficiency of the drivetrain/transmission is important because it influences the efficiency of the engine.

The Prius is a major achievement by Toyota: it is the first mass-produced HEV with the first available HEV-optimized engine. Argonne National Laboratory's Advanced Powertrain Test Facility has been testing the Prius for model validation and technology performance and assessment. A significant part of the Prius test program is focused on testing and mapping the engine. A short-length torque sensor was installed in the powertrain in-situ. The torque sensor data allow insight into vehicle operational strategy, engine utilization, engine efficiency, and specific emissions. This paper describes the design and process necessary to install a torque sensor in a vehicle and shows the high-fidelity data measured during chassis dynamometer testing. The engine was found to have a maximum thermodynamic efficiency of 36.4%. Emissions and catalyst efficiency maps were also produced.

Hybrid Electric Vehicles (HEVs) can be designed and operated to satisfy many different operational missions. The three most common HEV types differ with respect to component sizing and operational capabilities. However, HEV technology offers design opportunities beyond these three types. This paper presents a detailed HEV categorization process that can be used to describe unique HEV prototype designs entered in college and university-level HEV design competitions. We explored possible energy management strategies associated with designs that control the utilization of the two on-board energy sources and use the competition vehicles to illustrate various configurations and designs that affect the vehicle's capabilities. Experimental data is used to help describe the details of the power control strategies which determine how the engine and electric motor of HEV designs work together to provide motive power to the wheels.

This work examines the characteristics of a methanol fueled porous media burner, the principles of which may be used as a basis for a practical radiant heat source for an on-board catalytic methanol reformer. The burner uses a conventional engine port fuel injector designed for methanol use. The spray from the injector was impinged upon the bottom of a stack of two or three pieces of ceramic foam. The ceramics were 2.5 cm thick, 10 cm in diameter and were enclosed in a quartz cylinder for visualization. The upstream ceramic acted as a flame holder and the surface of the downstream ceramic was the radiation source. The range of air and fuel flow rates over which stable combustion was possible was investigated. Fuel flow rates between 0.12 and 0.48 gm/s were examined. Overall equivalence ratios between 0.65 and 0.2 resulted in stable combustion.

Predictions of the Fractal Engine Simulation code were compared with SI engine data in a previous paper. These comparisons were extremely good except for the single data set available at a low engine speed. Because of uncertainty regarding whether the lack of agreement for this case resulted from some difficulty with the experimental data or was due to lack of proper speed dependence in the model, additional comparisons are made for a range of speeds from 300-1500 rpm. The fractal burning model is a turbulence driven model (i.e., driven primarily by the turbulence intensity) that divides the combustion process into four sequential phases: 1) kernel formation, 2) early flame growth, 3) fully developed turbulent flame propagation, and 4) end of combustion. The kernel formation process was not included in the previous version of this model, but was found to be required to predict engine speed effects.

The results of continuing investigations of a new type of ignitor, the railplug, are reported. Previous studies have shown that railplugs can produce a high velocity jet that is driven both by electromagnetic and thermal forces and that the jet velocity is strongly affected by the railplug geometry and by the electronics characteristics of the follow-on circuit. The present research was intended to provide insights about both: 1) how to match the electronics characteristics to a given geometry and 2) how the geometry affects the jet velocity. It is found that faster current rise times result in higher plasma velocities but current pulses that are too short result in rapid deceleration of the plasma while it is still within the railplug. It is also found that a fundamental geometric parameter is the ratio of the inductance gradient to the volume trapped within the railplug: the larger L′/V, the faster the resulting combustion process.

Researchers in the field of turbulent combustion have found fractal geometry to be a useful tool for describing and quantifying the nature of turbulent flames. This paper describes and compares several techniques for the fractal analysis of two dimensional (2-D) turbulent flame images. Four methods of fractal analysis were evaluated: the Area Method, the Box Method, the Caliper Method, and the Area-Caliper Method. These techniques were first applied to a computer-generated fractal image having a known fractal dimension and known cut-offs. It was found that a “window” effect can cause the outer cut-off to be underestimated. The Caliper Method was found to suffer from noise arising from the statistical nature of the analysis. The Area-Caliper Method was found to be superior to the other methods. The techniques were applied to two types of flame images obtained in a spark ignition engine: Mie scattering from particles seeded in the flow and laser induced fluorescence of OH.

Laser Doppler velocimetry was used to make cycle-resolved velocity and turbulence measurements under motoring and firing conditions in a ported homogeneous charge S.I. engine. The engine had a flat pancake chamber with a compression ratio of 7.5. In one study, the effect of the intake velocity on TDC turbulence intensity was measured at 600, 1200, and 1800 rpm with three different intake flow rates at each speed. The TDC swirl ratio ranged from 2 to 6. The TDC turbulence intensities were found to be relatively insensitive to the intake velocity, and tended to scale more strongly with engine speed. For the combustion measurements, the engine was operated at 600, 1200, and 2400 rpm on stoichiometric and lean propane-air mixtures. Velocity measurements were made in swirling and non-swirling flows at several spatial locations on the midplane of the clearance height. The TDC swirl ratio was about 4. The measurements were made ahead, through, and behind the flame.

Laser Doppler velocimetry has been used to make cycle-resolved velocity and turbulence measurements in a homogeneous-charge, spark-ignition engine. The engine had a ported intake and disc-shaped chamber with a compression ratio of 7.5 to 1. It was operated at a speed of 1200 rpm and with a TDC swirl number of 4. A stoichiometric propane-air mixture was used, and ignition was near the wall. Measurements of the tangential velocity component were made in both firing and non-firing cycles at nine spatial locations along a radius 180 degrees downstream of the spark. The radial velocity component was also measured at four of the locations. All measurements were made in the center of the clearance height. Tangential component measurements were made as close as 0.5mm from the cylinder wall, and the radial component was measured as close as 1.5mm from the wall.

Laser Doppler velocimetry has been used to make cycle-resolved velocity and turbulence measurements in a homogeneous-charge, spark-ignition engine. The engine had a ported intake and disc-shaped chamber with a compression ratio of 8 to 1. It was operated at a speed of 1200 rpm and with a TDC swirl number of 4. A stoichiometric propane-air mixture was used, and ignition was near the wall. The velocity measurements were made at three spatial locations at the midpoint of the clearance height. Tests were made to determine whether the presence of the flame affected the accuracy of the velocity measurements. It was found that the ensemble-averaged mean velocity shows a small deviation, and the rms fluctuation intensity is significantly influenced, but the effects appear to be confined to the flame zone. Data rates were sufficiently high in the preflame and postflame regions to determine the velocity history in each cycle (cycle resolved).