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Software testing is all too often simply a bug hunt rather than a well-considered exercise in ensuring quality. A more methodical approach than a simple cycle of system-level test-fail-patch-test will be required to deploy safe autonomous vehicles at scale. The ISO 26262 development V process sets up a framework that ties each type of testing to a corresponding design or requirement document, but presents challenges when adapted to deal with the sorts of novel testing problems that face autonomous vehicles. This paper identifies five major challenge areas in testing according to the V model for autonomous vehicles: driver out of the loop, complex requirements, non-deterministic algorithms, inductive learning algorithms, and fail-operational systems.

The focus of the present study was to characterize Reactivity Controlled Compression Ignition (RCCI) using a single-fuel approach of gasoline and gasoline mixed with a commercially available cetane improver on a multi-cylinder engine. RCCI was achieved by port-injecting a certification grade 96 research octane gasoline and direct-injecting the same gasoline mixed with various levels of a cetane improver, 2-ethylhexyl nitrate (EHN). The EHN volume percentages investigated in the direct-injected fuel were 10, 5, and 2.5%. The combustion phasing controllability and emissions of the different fueling combinations were characterized at 2300 rpm and 4.2 bar brake mean effective pressure over a variety of parametric investigations including direct injection timing, premixed gasoline percentage, and intake temperature. Comparisons were made to gasoline/diesel RCCI operation on the same engine platform at nominally the same operating condition.

Cylinder liners exert a major influence on engine performance, reliability, durability and maintenance. Various combinations of nonmetallic reinforcements and coatings have been used to improve the tribological performance of sleeves or surfaces used in compressors and internal combustion engines in four stroke, two stroke and rotary configurations. In this paper we report the use of a hybrid composite containing silicon carbide and graphite in an aluminum alloy matrix to improve the performance of various small engines and compressors. Material properties of the base material, as well as comparative dynamometer testing, are presented.

Fuel spray atomization and breakup processes within a direct-injection spark-ignition (DISI) engine and outside the engine were modeled using a modified KIVA-3V code with improved spray models. The structures of the predicted sprays were qualitatively compared with planar images. The considered sprays were created by a prototype pressure-swirl injector and the planar images were obtained by laser sheet imaging in an optical DISI engine. In the out-of-engine case, the spray was injected into atmospheric air, and was modeled in a two dimensional bomb. In the engine case, the injection started from 270° ATDC, and full 3-D computations in the same engine were performed. In both cases, two liquid injection pressure conditions were applied, that is, 3.40 MPa and 6.12 MPa. The model gives good prediction of the tip penetration, and external spray shape, but the internal structure prediction has relatively lower accuracy, especially near the spray axis.

While Low Temperature Combustion (LTC) strategies such as Reactivity Controlled Compression Ignition (RCCI) exhibit high thermal efficiency and produce low NOx and soot emissions, low load operation is still a significant challenge due to high unburnt hydrocarbon (UHC) and carbon monoxide (CO) emissions, which occur as a result of poor combustion efficiencies at these operating points. Furthermore, the exhaust gas temperatures are insufficient to light-off the Diesel Oxidation Catalyst (DOC), thereby resulting in poor UHC and CO conversion efficiencies by the aftertreatment system. To achieve exhaust gas temperature values sufficient for DOC light-off, combustion can be appropriately phased by changing the ratio of gasoline to diesel in the cylinder, or by burning additional fuel injected during the expansion stroke through post-injection.

THIS paper discusses a method of measuring compression temperature by means of the absorption of light. An optical-electronic system measures the change in color of a trace of iodine gas that has been added to the intake mixture. From these measurements the temperature of the iodine and by inference, the temperature of the gases, is determined. The apparatus used is described briefly and the test results obtained in measuring compression and end-gas temperatures in a spark-ignition engine are also presented.

An overview of a design methodology based on finite element and fatigue analyses is described for the design of welded structures. Fatigue life is a primary design consideration for agricultural equipment structural members. The re-design of an agricultural implement frame and hitch assembly is used to illustrate the methodology for optimal design and improved fatigue life. A description of the finite element mode of the agricultural implement and the simulated loading history are described. Results from finite element analysis are used to optimize the frame member sizes and calculate the fatigue strength characteristics. This design analysis strategy provides improved fatigue life characteristics for the implement frame or welded structure.

This paper takes a step towards eliminating the automobile industry's dependence on “seat of the pants” ride analysis by investigating the correlation between vertical acceleration and passenger comfort. To do this, it first develops a relationship between accelerometer data and ride comfort on a controlled test surface, and then extends this relationship to actual road conditions. To illustrate the usefulness of this approach, a simple, typical problem in more detailed ride analysis is briefly considered.

There has been an increasing interest in exploring the potential to reduce energy consumption of future connected and automated vehicles. People have extensively studied various eco-driving implementations that leverage preview information provided by on-board sensors and connectivity, as well as the control authority enabled by automation. Quantitative real-world evaluation of eco-driving benefits is a challenging task. The standard regulatory driving cycles used for measuring exhaust emissions and fuel economy are not truly representative of real-world driving, nor for capturing how connectivity and automation might influence driving trajectories. To adequately consider real-world driving behavior and potential “off-cycle” impacts, this paper presents four collaborative evaluation methods: large-scale simulation, in-depth simulation, vehicle-in-the-loop testing, and vehicle road testing.

A method of calculating mass burning rates for a single cylinder spark-ignition combustion engine based on experimentally obtained pressure-time diagrams was used to analyze the effects of fuel-air ratio, engine speed, spark timing, load, and cyclic cylinder pressure variations on mass burning rates and engine output. A study of the effects on mass burning rates by cyclic pressure changes showed the low pressure cycles were initially slow burning cycles. Although large cyclic cylinder pressure variations existed in the data the cyclic variations in imep were relatively small.

The EcoCAR Mobility Challenge (EMC) is the latest edition of the Advanced Vehicle Technology Competition (AVTC) series sponsored by the US Department of Energy. This competition challenges 11 North American universities to redesign a stock 2019 Chevrolet Blazer into an energy-efficient, SAE level 2-autonomous mild hybrid electric vehicle (mHEV) for use in the Mobility as a Service (MaaS) market. The Mississippi State University (MSU) team designed a P4 electric powertrain with an 85kW (113.99 HP) permanent magnet synchronous machine (PMSM) powered by a custom 5.4 kWh lithium-ion energy storage system. To maximize energy efficiency, Model Based Design concepts were leveraged to optimize the overall gear ratio for the P4 system. To accommodate this optimized ratio in the stock vehicle, a custom offset gearbox was designed that links the PMSM to the rear drive module.

Control of the timing and magnitude of heat release is one of the biggest challenges for premixed compression ignition, especially when attempting to operate at high load. Single-fuel strategies such as partially premixed combustion (PPC) use direct injection of gasoline to stratify equivalence ratio and retard heat release, thereby reducing pressure rise rate and enabling high load operation. However, retarding the heat release also reduces the maximum work extraction, effectively creating a tradeoff between efficiency and noise. Dual-fuel strategies such as reactivity controlled compression ignition (RCCI) use premixed gasoline and direct injection of diesel to stratify both equivalence ratio and fuel reactivity, which allows for greater control over the timing and duration of heat release. This enables combustion phasing closer to top dead center (TDC), which is thermodynamically favorable.

Life histories of droplets evaporating on a hot plate under pressure were obtained. The curves are similar to those obtained by one investigator at atmospheric pressure but are displaced to higher temperatures at higher pressures. Similarities between boiling heat transfer and the life history curves are pointed out. Also, that the liquid will most probably reach critical pressure and temperature at temperatures existing inside an engine. The effects of reaching the critical temperature on heat transfer and on vaporization and diffusion are discussed.

In Equation 10, there should be a plus sign between the first summation term and the quantity in brackets. The acceleration of the participant's vehicle was varied from −0.04 m/s2 to +0.06 m/s2 linearly as a function of the angle of the gas pedal with a 0.1-second delay.

This paper investigates the effect of E85 on load expansion and FTP modal point emissions indices under reactivity controlled compression ignition (RCCI) operation on a light-duty multi-cylinder diesel engine. A General Motors (GM) 1.9L four-cylinder diesel engine with the stock compression ratio of 17.5:1, common rail diesel injection system, high-pressure exhaust gas recirculation (EGR) system and variable geometry turbocharger was modified to allow for port fuel injection with gasoline or E85. Controlling the fuel reactivity in-cylinder by the adjustment of the ratio of premixed low-reactivity fuel (gasoline or E85) to direct injected high reactivity fuel (diesel fuel) has been shown to extend the operating range of high-efficiency clean combustion (HECC) compared to the use of a single fuel alone as in homogeneous charge compression ignition (HCCI) or premixed charge compression ignition (PCCI).

This research investigates how the handling of mixing and heat transfer in a multi-zone kinetic solver affects the prediction of carbon monoxide and hydrocarbon emissions for simulations of HCCI engine combustion. A detailed kinetics multi-zone model is now more closely coordinated with the KIVA3V computational fluid dynamics code for simulation of the compression and expansion processes. The fluid mechanics is solved with high spatial and temporal resolution (40,000 cells). The chemistry is simulated with high temporal resolution, but low spatial resolution (20 computational zones). This paper presents comparison of simulation results using this enhanced multi-zone model to experimental data from an isooctane HCCI engine.

This paper presents the results from experiments and Computational Fluid Dynamics (CFD) simulations performed to understand the impact of piston geometry on ignition delay for Dimethyl Ether (DME)/air mixtures inside a Rapid Compression Machine (RCM). Three piston shapes and two dilution ratios are studied using CFD simulations validated by experiments. The three piston geometries under consideration are: a flat piston, a piston with an enlarged crevice, and a bowl piston. Key phenomena analyzed in the study include fluid flow patterns, heat transfer, temperature homogeneity of the mixture, and ignition delay. The CFD model provides reasonable predictions of ignition delay when compared with experimental data. Simulations indicate that flat and bowl pistons show similar heat transfer, ignition delay, and combustion characteristics, while the enlarged creviced piston shows lower peak temperatures and a cooler mixture core due to higher wall heat transfer.

The effect of direct-injected fuel on particle size distributions (PSDs) of particulate matter emitted from dual-fuel combustion strategies was investigated. The PSD data were acquired from a light-duty single-cylinder diesel engine operated using conventional diesel combustion (CDC) and two diesel/natural gas dual-fuel combustion strategies. Three different direct-injection (DI) fuels (diesel, 2,6,10-trimethyldodecane, and a primary reference fuel blend) and two different injector nozzles were studied. The DI fuels were chosen to have similar energy and ignition characteristics (heat of combustion and cetane number) but different physical and chemical properties (volatility, aromatics %, viscosity, density). The two nozzles (with different orifice diameter and spray angle) allowed a wide range in DI fuel quantity for the dual-fuel combustion strategies.

The effects of numerical methodology in defining the initial conditions and simulating the compression stroke in D.I. diesel engine CFD computations are studied. Lumped and pointwise approaches were adopted in assigning the initial conditions at IVC. The lumped approach was coupled with a two-dimensional calculation of the compression stroke. The pointwise methodology was based on the results of an unsteady calculation of the intake stroke performed by using the STAR-CD code in the realistic engine and port geometry. Full engine and 60 deg. sector meshes were used in the compression stroke calculations in order to check the accuracy of the commonly applied axi-symmetric fluid dynamics assumption. Analysis of the evolution of the main fluid dynamics parameters revealed that local conditions at the time of injection strongly depend on the numerical procedure adopted.

Low pressure EGR offers greater effectiveness and flexibility for turbocharging and improved heat transfer compared to high pressure EGR systems. These characteristics have been shown to provide potential for further NOx, soot, and fuel consumption reductions in modern diesel engines. One of the drawbacks is reduced transient response capability due to the long EGR path. This can be largely mitigated by combining low pressure and high pressure loops in a hybrid EGR system, but the changes in transient response must be considered in the design of an effective control strategy. The effect of low pressure EGR on transient emissions was evaluated using two different combustion strategies over a variety of transient events. Low pressure EGR was found to significantly lengthen the response time of intake oxygen concentration following a transient event, which can have a substantial effect on emissions formation.