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Technical Paper

Benefits and Application Bandwidth of Phenolic Piston Material in Opposed Piston Calipers

2019-09-15
2019-01-2123
The use of reinforced phenolic composite material in application to hydraulic pistons for brake calipers has been well established in the industry - for sliding calipers (and certain fixed calipers with high piston length to diameter ratios). For decades, customers have enjoyed lower brake fluid temperatures, mass savings, improved corrosion resistance, and smoother brake operation (less judder). However, some persistent concerns remain about the use of phenolic materials for opposed piston calipers. The present work explores two key questions about phenolic piston application in opposed piston calipers. Firstly, do opposed piston calipers see similar benefits? Do high performance aluminum bodied calipers, where the piston may no longer be a dominant heat flow path into the fluid (due to a large amount of conduction and cooling enabled by the housing), still enjoy fluid temperature reductions?
Technical Paper

Limitations of Sector Mesh Geometry and Initial Conditions to Model Flow and Mixture Formation in Direct-Injection Diesel Engines

2019-04-02
2019-01-0204
Sector mesh modeling is the dominant computational approach for combustion system design optimization. The aim of this work is to quantify the errors descending from the sector mesh approach through three geometric modeling approaches to an optical diesel engine. A full engine geometry mesh is created, including valves and intake and exhaust ports and runners, and a full-cycle flow simulation is performed until fired TDC. Next, an axisymmetric sector cylinder mesh is initialized with homogeneous bulk in-cylinder initial conditions initialized from the full-cycle simulation. Finally, a 360-degree azimuthal mesh of the cylinder is initialized with flow and thermodynamics fields at IVC mapped from the full engine geometry using a conservative interpolation approach. A study of the in-cylinder flow features until TDC showed that the geometric features on the cylinder head (valve tilt and protrusion into the combustion chamber, valve recesses) have a large impact on flow complexity.
Technical Paper

Development of the TOP TIERTM Diesel Standard

2019-04-02
2019-01-0264
The TOP TIERTM Diesel fuel standard was first established in 2017 to promote better fuel quality in marketplace to address the needs of diesel engines. It provides an automotive recommended fuel specification to be used in tandem with regional diesel fuel specifications or regulations. This fuel standard was developed by TOP TIERTM Diesel Original Equipment Manufacturer (OEM) sponsors made up of representatives of diesel auto and engine manufacturers. This performance specification developed after two years of discussions with various stakeholders such as individual OEMs, members of Truck and Engine Manufacturers Association (EMA), fuel additive companies, as well as fuel producers and marketers. This paper reviews the major aspects of the development of the TOP TIERTM Diesel program including implementation and market adoption challenges.
Technical Paper

A Mechanism-Based Thermomechanical Fatigue Life Assessment Method for High Temperature Engine Components with Gradient Effect Approximation

2019-04-02
2019-01-0536
High temperature components in internal combustion engines and exhaust systems must withstand severe mechanical and thermal cyclic loads throughout their lifetime. The combination of thermal transients and mechanical load cycling results in a complex evolution of damage, leading to thermomechanical fatigue (TMF) of the material. Analytical tools are increasingly employed by designers and engineers for component durability assessment well before any hardware testing. The DTMF model for TMF life prediction, which assumes that micro-crack growth is the dominant damage mechanism, is capable of providing reliable predictions for a wide range of high-temperature components and materials in internal combustion engines. Thus far, the DTMF model has employed a local approach where surface stresses, strains, and temperatures are used to compute damage for estimating the number of cycles for a small initial defect or micro-crack to reach a critical length.
Technical Paper

Constitutive Modeling and Thermomechanical Fatigue Life Predictions of A356-T6 Aluminum Cylinder Heads Considering Ageing Effects

2019-04-02
2019-01-0534
Cast aluminum alloys are frequently used as materials for cylinder head applications in internal combustion gasoline engines. These components must withstand severe cyclic mechanical and thermal loads throughout their lifetime. Reliable computational methods allow for accurate estimation of stresses, strains, and temperature fields and lead to more realistic Thermomechanical Fatigue (TMF) lifetime predictions. With accurate numerical methods, the components could be optimized via computer simulations and the number of required bench tests could be reduced significantly. These types of alloys are normally optimized for peak hardness from a quenched state that maximizes the strength of the material. However due to high temperature exposure, in service or under test conditions, the material would experience an over-ageing effect that leads to a significant reduction in the strength of the material.
Technical Paper

Development of a Low Loss Clutch for CVT Reverse Function

2019-04-02
2019-01-0774
Continuously variable transmissions (CVT) provide superior fuel economy by enabling internal combustion engines to operate at their “sweet spots”. However, there is still potential to improve CVT system’s mechanical efficiency, and further enhance vehicle-level fuel economy. In the past, extensive research work has focused on the core continuously variator unit (CVU) that includes pulleys and a belt or chain. Another thread of research has centered on optimization of CVT clamping force control to reduce hydraulic system loss. Nonetheless, to the best of our knowledge, very little research has looked into the planetary gear sets and clutches that enable the CVT system to switch between forward, neutral and reverse gears. The state-of-the-art reverse clutch usually consists of multiple friction and steel plates, and is normally open during all forward driving maneuvers. The relative speed between friction and steel plates is identical to turbine speed, which generate spin loss.
Technical Paper

Combustion-Timing Control of Low-Temperature Gasoline Combustion (LTGC) Engines by Using Double Direct-Injections to Control Kinetic Rates

2019-04-02
2019-01-1156
Low-temperature gasoline combustion (LTGC) engines can provide high efficiencies and extremely low NOx and particulate emissions, but controlling the combustion timing remains a challenge. This paper explores the potential of Partial Fuel Stratification (PFS) to provide fast control of CA50 in an LTGC engine. Two different compression ratios are used (CR=16:1 and 14:1) that provide high efficiencies and are compatible with mixed-mode SI-LTGC engines. The fuel used is a research grade E10 gasoline (RON 92, MON 85) representative of a regular-grade market gasoline found in the United States. The fuel was supplied with a gasoline-type direct injector (GDI) mounted centrally in the cylinder. To create the PFS, the GDI injector was pulsed twice each engine cycle. First, an injection early in the intake stroke delivered the majority of the fuel (70 - 80%), establishing the minimum equivalence ratio in the charge.
Technical Paper

Efficiency Evaluation of Lower Viscosity ATF in a Planetary Automatic Transmission for Improved Fuel Economy

2019-04-02
2019-01-1296
With continued industry focus on reducing parasitic transmission and driveline losses, detailed studies are required to quantify potential enablers to improve vehicle fuel economy. Investigations were undertaken to understand the influence of lower viscosity Automatic Transmission Fluids (ATF) on transmission efficiency as compared with conventional fluids. The objectives of this study were to quantify the losses of lower viscosity ATF as compared with conventional ATF, and to understand the influence of ATF properties including viscosities, base oil types, and additive packages on fuel efficiency. The transmission efficiency investigations were conducted on a test bench following a vehicle-based break-in of the transmission using a prescribed drive cycle on a chassis dynamometer. At low temperature, the lower viscosity ATF showed a clear advantage over the conventional ATF in both spin loss and loaded efficiency evaluations.
Technical Paper

Tooling Effects on Edge Stretchability of AHSS in Mechanical Punching

2019-04-02
2019-01-1086
Edge stretchability reduction induced by mechanical trimming is a critical issue in advanced high strength steel applications. In this study, the tooling effects on the trimmed edge damage were evaluated by the specially designed in-plane hole expansion test with the consideration of three punch geometries (flat, conical, and rooftop), three cutting clearances (6%, 14%, and 20%) and two materials grades (DP980 and DP1180). Two distinct fracture initiation modes were identified with different testing configurations, and the occurrence of each fracture mode depends on the tooling configurations and materials grades. Digital Image Correlations (DIC) measurements indicate the materials are subject to different deformation modes and the various stress conditions, which result in different fracture initiation locations.
Journal Article

Electrified Drive-Unit Parametric Mechanical-Loss Model Development and Calibration

2019-04-02
2019-01-1298
As the automotive industry vies to meet progressively more stringent global CO2 regulations in a cost-effective manner, electrified drive system cost and losses must be reduced. To this end, a parametric Drive Unit (DU) mechanical-loss model was developed to aid in the design and development of electrified propulsion systems, where the total propulsion system cost and DU losses can be directly linked (e.g., Hybrid Electric Vehicle (HEV) motor/inverter/engine content, or Battery Electric Vehicle (BEV) battery size). Many DUs for electrified propulsion systems are relatively “simple” drive systems, consisting of gears, bearings, shafts, lip seals, and an electric motor(s), but without clutches, high-pressure lube systems, or chains/belts as found in conventional automatic transmissions. The DU loss model described in this paper studies these simple DUs, with the mechanical losses dissected into 10 loss components.
Technical Paper

Evaluation of V2V Reception Cadence- A New Metric for System Level Performance Analysis

2019-01-16
2019-01-0102
Vehicle to Everything (V2X) communication is a prominent solution for active safety collision avoidance and for providing autonomous vehicles Non-Line of Sight (NLOS) capabilities. For safety purposes, it is essential the V2X technology would support communication between all road users, e.g., Vehicles (V2V), pedestrians (V2P) and road infrastructure (V2I). Hence, the efficiency of a V2V communication solution should be evaluated through system level performance. In addition, the examined performance metrics need to reflect safety related properties. Metrics as Packet Reception Ratio (PRR) and transmission latencies, which are commonly used to assess V2X system’s functionality, aren’t enough since reception latencies are overlooked. The latter is crucial in ensuring messages would reach their destination on time to avoid hazardous incidents. The reception cadence may be much lower than this of the transmission due to various phenomenon (e.g. channel congestion).
Technical Paper

Brake System Design for Dedicated BEV Architectures

2018-10-05
2018-01-1870
As fossil fuels dwindle and more electric vehicles enter the market, there is an opportunity to reevaluate the standard brake system. This paper will discuss and compare the differences in brake system sizing between a non-regenerative braking internal combustion engine vehicle and a dedicated battery electric vehicle with regenerative braking. It will use a model derived from component dynamometer testing and vehicle test data of a mid-size production vehicle. The model will be modified for the mass and regenerative braking capabilities of a battery electric vehicle. The contribution of regenerative braking energy will be analyzed and compared to show its impact on component sizing, thermal sizing, and lining life. The detailed design study will calculate the parameters for caliper, rotor design, actuation, etc., that are optimized for 100% regen enabled vehicles.
Technical Paper

Bowl Geometry Effects on Turbulent Flow Structure in a Direct Injection Diesel Engine

2018-09-10
2018-01-1794
Diesel piston bowl geometry can affect turbulent mixing and therefore it impacts heat-release rates, thermal efficiency, and soot emissions. The focus of this work is on the effects of bowl geometry and injection timing on turbulent flow structure. This computational study compares engine behavior with two pistons representing competing approaches to combustion chamber design: a conventional, re-entrant piston bowl and a stepped-lip piston bowl. Three-dimensional computational fluid dynamics (CFD) simulations are performed for a part-load, conventional diesel combustion operating point with a pilot-main injection strategy under non-combusting conditions. Two injection timings are simulated based on experimental findings: an injection timing for which the stepped-lip piston enables significant efficiency and emissions benefits, and an injection timing with diminished benefits compared to the conventional, re-entrant piston.
Technical Paper

System Engineering for Automated Software Update of Automotive Electronics

2018-04-03
2018-01-0750
In traditional automotive electronic design, software update has been a component oriented, manual process rather than a systematic designed in capability suitable for automation. In recent days as software content in vehicles grow, the need to update software in vehicles more frequently is becoming a necessity. Moreover, additional attributes for software updates, for example timely delivery of security related update for vehicles, desire to add features using software update, control cost of software updates, etc., requires a system engineered design rather than a component oriented approach. As the automobile domain utilizes various means of mobility (Combustion Engine, Hybrid, Battery, etc.) and various functional domains (Infotainment, Safety, Mobility, Telematics, ADAS (Advance Driving Assist service), Autonomous, etc.), to control the overall cost of future software update for such a diverse environment, it is beneficial to introduce automation in the software update process.
Technical Paper

Spark Assist for CA50 Control and Improved Robustness in a Premixed LTGC Engine – Effects of Equivalence Ratio and Intake Boost

2018-04-03
2018-01-1252
Low-temperature gasoline combustion (LTGC) engines can deliver high efficiencies, with ultra-low emissions of nitrogen oxides (NOx) and particulate matter (PM). However, controlling the combustion timing and maintaining robust operation remains a challenge for LTGC engines. One promising technique to overcoming these challenges is spark assist (SA). In this work, well-controlled, fully premixed experiments are performed in a single-cylinder LTGC research engine at 1200 rpm using a cylinder head modified to accommodate a spark plug. Compression ratios (CR) of 16:1 and 14:1 were used during the experiments. Two different fuels were also tested, with properties representative of premium- and regular-grade market gasolines. SA was found to work well for both CRs and fuels. The equivalence ratio (ϕ) limits and the effect of intake-pressure boost on the ability of SA to compensate for a reduced Tin were studied. For the conditions studied, ϕ=0.42 was found to be most effective for SA.
Technical Paper

Supervisory Model Predictive Control of a Powertrain with a Continuously Variable Transmission

2018-04-03
2018-01-0860
This paper describes the design of a supervisory multivariable constrained Model Predictive Control (MPC) system for driver requested axle torque tracking with real-time fuel economy optimization that is scheduled for production by General Motors starting in 2018. The control system has been conceived and co-developed by General Motors and ODYS. The control approach consists of a set of linear MPC controllers scheduled in real-time based on powertrain operating conditions. For each MPC controller, a linear model is obtained by system identification with vehicle and dynamometer data. The supervisory MPC coordinates in real time desired Continuously Variable Transmission (CVT) ratio and desired engine torque to satisfy the system requirements, based on estimates of axle torque and engine fuel rate, by solving a constrained optimization problem at each sampling step. Each linear MPC controller is equipped with a Kalman filter to reconstruct the system state from available measurements.
Technical Paper

Model Predictive Control of Turbocharged Gasoline Engines for Mass Production

2018-04-03
2018-01-0875
This paper describes the design of a multivariable, constrained Model Predictive Control (MPC) system for torque tracking in turbocharged gasoline engines scheduled for production by General Motors starting in calendar year 2018. The control system has been conceived and co-developed by General Motors and ODYS. The control approach consists of a set of linear MPC controllers scheduled in real time based on engine operating conditions. For each MPC controller, a linear model is obtained by system identification with data collected from engines. The control system coordinates throttle, wastegate, intake and exhaust cams in real time to track a desired engine torque profile, based on measurements and estimates of engine torque and intake manifold pressure.
Technical Paper

Design and Control of Torque Feedback Device for Driving Simulator Based on MR Fluid and Coil Spring Structure

2018-04-03
2018-01-0689
Since steering wheel torque feedback is one of the crucial factors for drivers to gain road feel and ensure driving safety, it is especially important to simulate the steering torque feedback for a driving simulator. At present, steering wheel feedback torque is mainly simulated by an electric motor with gear transmission. The torque response is typically slow, which can result in drivers’ discomfort and poor driving maneuverability. This paper presents a novel torque feedback device with magnetorheological (MR) fluid and coil spring. A phase separation control method is also proposed to control its feedback torque, including spring and damping torques respectively. The spring torque is generated by coil spring, the angle of coil spring can be adjusted by controlling a brushless DC motor. The damping torque is generated by MR fluid, the damping coefficient of MR fluid can be adjusted by controlling the current of excitation coil.
Technical Paper

NVH Design, Analysis and Optimization of Chevrolet Bolt Battery Electric Vehicle

2018-04-03
2018-01-0994
A multi-stage system level method is used to design, optimize and enhance electric motor NVH performance of General Motors’ Chevrolet Bolt battery electric vehicle (BEV). First, the rotor EM (electromagnetic) design optimizes magnet placement between adjacent poles asymmetrically, along with a pair of small slots stamped near the rotor outer surface to lower torque ripple and radial force. The size and placement of stator slot openings under each pole are optimized to lower torque ripple and radial force. Next, motor stator level FE (Finite Element) analysis and modal test correlation are performed to benchmark the orthotropic stator material properties and accurately predict modal results within 7% error below 2 kHz. Furthermore, tangential and radial EM forces are applied on motor-in-fixture subsystem FE model, which predicts surface vibration and pseudo sound power on the motor housing.
Technical Paper

The Development and Evaluation of Robust Combustion Systems for Miller Cycle Engines

2018-04-03
2018-01-1416
Miller Cycle engines employ a high expansion ratio to achieve high part-load efficiency, while minimizing knock sensitivity by using valve events that limit the effective compression ratio. The Miller effect may be achieved using either early or late intake valve closure. Combustion systems for these engines must be carefully designed to obtain adequate trapped charge to achieve full-load objectives as well as charge motion characteristics supporting good mixture preparation and flame propagation. This paper summarizes the results of a holistic project tasked with developing robust combustion systems for both early and late intake valve closure strategies. Based on best practices from conventional engines and preliminary Miller cycle requirements, a series of combustion systems was designed. These were analyzed using 3-dimensional computational fluid dynamics and those showing favorable combustion characteristics were experimentally evaluated using a modular single cylinder engine.
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