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Technical Paper

Thermal Management of a Hybrid Vehicle Using a Heat Pump

2019-04-02
2019-01-0502
This paper presents the thermal management of a hybrid vehicle (HV) using a heat pump system in cold weather. One advantage of an HV is the high efficiency of the vehicle system provided by the coupling and optimal control of an electric motor and an engine. However, in a conventional HV, fuel economy degradation is observed in cold weather because delivering heat to the passenger cabin using the engine results in a reduced efficiency of the vehicle system. In this study, a heat pump, combined with an engine, was used for thermal management to decrease fuel economy degradation. The heat pump is equipped with an electrically driven compressor that pumps ambient heat into a water-cooled condenser. The heat generated by the engine and the heat pump is delivered to the engine and the passenger cabin because the engine needs to warm up quickly to reduce emissions and the cabin needs heat to provide thermal comfort.
Technical Paper

Research of Knocking Deterioration due to Accumulated Carbon Deposits on Piston Surfaces

2019-04-02
2019-01-1141
The quantity of heavy components in fuel is increasing as automotive fuels diversify, and engine oil formulations are becoming more complex. These trends result in the formation of larger amounts of carbon deposits as reaction byproducts during combustion, potentially worsening the susceptibility of the engine to knock [1]. The research described in this paper aimed to identify the mechanism that causes knocking to deteriorate due to carbon deposits in low to medium engine load ranges, which are mainly used when the vehicle drives off and accelerates. With this objective, the cylinder temperature and pressure with and without deposits were measured, and it was found that knocking deteriorates in a certain range of ignition timing.
Technical Paper

Using Chemical Kinetics to Understand Effects of Fuel Type and Compression Ratio on Knock-Mitigation Effectiveness of Various EGR Constituents

2019-04-02
2019-01-1140
Exhaust gas recirculation (EGR) can be used to mitigate knock in SI engines. However, experiments have shown that the effectiveness of various EGR constituents to suppress knock varies with fuel type and compression ratio (CR). To understand some of the underlying mechanisms by which fuel composition, octane sensitivity (S), and CR affect the knock-mitigation effectiveness of EGR constituents, the current paper presents results from a chemical-kinetics modeling study. The numerical study was conducted with CHEMKIN, imposing experimentally acquired pressure traces on a closed reactor model. Simulated conditions include combinations of three RON-98 (Research Octane Number) fuels with two octane sensitivities and distinctive compositions, three EGR diluents, and two CRs (12:1 and 10:1). The experimental results point to the important role of thermal stratification in the end-gas to smooth peak heat-release rate (HRR) and prevent acoustic noise.
Technical Paper

Development of Low Pressure and High Performance GPF Catalyst

2018-04-03
2018-01-1261
Awareness of environmental protection with respect to the particulate number (PN) in the exhaust emissions of gasoline direct injection (GDI) engine vehicles has increased. In order to decrease the emission of particulate matter (PM), suppressing emissions by improving engine combustion, and/or filtering PM with a gasoline particulate filter (GPF) is effective. This paper describes the improvement of the coated GPF to reduce pressure drop while securing three-way performance and PN filtration efficiency. It was necessary to load a certain amount of washcoat on the GPF to add the three-way function, but this led to an increase in pressure drop that affected engine power. The pressure drop was influenced by the gas permeation properties of the filter wall.
Technical Paper

Development of CFD Inverse Analysis Technology Targeting Heat or Concentration Performance Using the Adjoint Method and Its Application to Actual Components

2018-04-03
2018-01-1033
To resolve two major problems of conventional CFD-based shape optimization technology: (1) dependence of the outcome on the selection of design parameters, and (2) high computational costs, two types of innovative inverse analysis technologies based on a mathematical theory called the Adjoint Method were developed in previous studies for maximizing an arbitrary hydrodynamic performance aspect as the cost function: surface geometry deformation sensitivity analysis to identify the locations to be modified, and topology optimization to generate an optimal shape. Furthermore, these technologies were extended to transient flows by the application of the transient Adjoint Method theory. However, there are many cases around flow path shapes in vehicles where performance with respect to heat or concentration, such as the total amount of heat transfer or the flow rate of a specific gas component, is very important.
Technical Paper

New 2.0L I4 Gasoline Direct Injection Engine with Toyota New Global Architecture Concept

2018-04-03
2018-01-0370
Toyota Motor Corporation has developed a new 2.0L Inline 4- Cylinder (I4) Gasoline Direct Injection Engine, the second Naturally Aspirated (NA) engine of the Toyota New Global Architecture (TNGA) engine series, to meet our customers’ expectations for drivability, performance, and fuel economy. The high speed combustion technologies adopted previously in our 2.5 L NA conventional and Hybrid Vehicle (HV) engines for the 2018 Toyota Camry are necessary for high engine power and thermal efficiency. To adopt our high speed combustion technology on engines with different displacements, the turbulence intensity has been defined as the target index of combustion speed. The basic engine structure has been revised by using Computational Fluid Dynamics (CFD) analysis to achieve the combustion target.
Journal Article

A Study on Optimal Powertrain Sizing of Plugin Hybrid Vehicles for Minimizing Criteria Emissions Associated with Cold Starts

2018-04-03
2018-01-0406
Plugin hybrid electric vehicles (PHEVs) have several attractive features in terms of reduction of greenhouse gas (GHG) emissions. Compared to conventional vehicles (CVs) that only have an internal combustion engine (ICE), PHEVs have better energy efficiency like regular hybrids (HEVs), allow for electrifying an appreciable portion of traveled miles, and have no range anxiety issues like battery-only electric vehicles (BEVs). However, in terms of criteria emissions (e.g., NOx, NMOG, HC), it is unclear if PHEVs are any better than HEVs or CVs. Unlike GHG emissions, criteria emissions are not continuously emitted in proportional quantities to fossil fuel consumption. Rather, the amount and type of criteria emissions is a rather complex function of many factors, including type of fuel, ICE temperature, speed and torque, catalyst temperature, as well as the ICE controls (e.g., fuel-to-air ratio, valve and ignition timing).
Technical Paper

The Effect of Gasoline Metallic Additives on Low Speed Pre-Ignition

2018-04-03
2018-01-0936
Methylcyclopentadienyl manganese tricarbonyl (MMT) is used as an octane-enhancing metallic additive for unleaded gasoline which can prevent engine knock by proactive reaction with the hydrocarbon free radicals before starting the auto-ignition of hydrocarbons. However it has been pointed out that MMT causes automotive catalysts clogging and spark plug severely fouling. Therefore, many countries have fuel standards that prohibit or limit the usage of MMT. Nevertheless, some countries still use MMT as there are no restrictions imposed by fuel standards. As mentioned in several papers, metallic additives of engine oil such as calcium cause an abnormal combustion phenomenon called low-speed pre-ignition (LSPI) in turbocharged spark ignition engines. In contrast, the effect of metallic additives of gasoline such as MMT on LSPI has not been studied.
Journal Article

Development of Engine Lubrication System with New Internal Gear Fully Variable Discharge Oil Pump

2017-10-08
2017-01-2431
Over the past decades, the automotive industry has made significant efforts to improve engine fuel economy by reducing mechanical friction. Reducing friction under cold conditions is becoming more important in hybrid vehicle (HV) and plug-in hybrid vehicle (PHV) systems due to the lower oil temperatures of these systems, which results in higher friction loss. To help resolve this issue, a new internal gear fully variable discharge oil pump (F-VDOP) was developed. This new oil pump can control the oil pressure freely over a temperature range from -10°C to hot conditions. At 20°C, this pump lowers the minimum main gallery pressure to 100 kPa, thereby achieving a friction reduction effect of 1.4 Nm. The developed oil pump achieves a pressure response time constant of 0.17 seconds when changing the oil pressure from 120 kPa to 200 kPa at a temperature of 20°C and an engine speed of 1,600 rpm.
Journal Article

A CFD Analysis Method for Prediction of Vehicle Exterior Wind Noise

2017-03-28
2017-01-1539
High frequency wind noise caused by turbulent flow around the front pillars of a vehicle is an important factor for customer perception of ride comfort. In order to reduce undesirable interior wind noise during vehicle development process, a calculation and visualization method for exterior wind noise with an acceptable computational cost and adequate accuracy is required. In this paper an index for prediction of the strength of exterior wind noise, referred to as Exterior Noise Power (ENP), is developed based on an assumption that the acoustic power of exterior wind noise can be approximated by the far field acoustic power radiated from vehicle surface. Using the well-known Curle’s equation, ENP can be represented as a surface integral of an acoustic intensity distribution, referred to as Exterior Noise Power Distribution (ENPD). ENPD is estimated from turbulent surface pressure fluctuation and mean convective velocity in the vicinity of the vehicle surface.
Journal Article

Theoretical Study on Spray Design for Small-Bore Diesel Engine (Second Report)

2017-03-28
2017-01-0704
Generally, soot emissions increase in diesel engines with smaller bore sizes due to larger spray impingement on the cavity wall at a constant specific output power. The objective of this study is to clarify the constraints for engine/nozzle specifications and injection conditions to achieve the same combustion characteristics (such as heat release rate and emissions) in diesel engines with different bore sizes. The first report applied the geometrical similarity concept to two engines with different bore sizes and similar piston cavity shapes. The smaller engine emitted more smoke because air entrainment decreases due to the narrower spray angle. A new spray design method called spray characteristics similarity was proposed to suppress soot emissions. However, a smaller nozzle diameter and a larger number of nozzle holes are required to maintain the same spray characteristics (such as specific air-entrainment and penetration) when the bore size decreases.
Technical Paper

New Combustion and Powertrain Control Technologies for Fun-to-Drive Dynamic Performance and Better Fuel Economy

2017-03-28
2017-01-0589
Toyota Motor Corporation has developed a new series of engines under the Toyota New Global Architecture (TNGA) design philosophy, which aims to satisfy customer requirements for both fun-to-drive dynamic performance and better fuel economy by adopting a high-speed combustion concept to improve thermal efficiency and specific power. This new engine series achieves a maximum engine thermal efficiency of 40%, a specific power ratio of 60 kW/l, and lower emissions by combining high-speed combustion and a high compression ratio with a high-tumble intake port, high-energy ignition coil, high-pressure multi-hole nozzle direct injector, and new electrical variable valve timing (VVT). The first engine in this series is a new 4-cylinder 2.5-liter gasoline naturally aspirated engine for use in passenger cars alongside a new TNGA 8-speed automatic transmission, which was introduced for minivans and SUVs in the U.S. market in 2016.
Technical Paper

New Exhaust Emission Control System with Two A/F Sensors

2017-03-28
2017-01-0917
Exhaust systems must satisfy a wide range of requirements, including lowering emissions to comply with future fuel economy and emissions regulations. To help meet these requirements, new emissions control systems have been developed today. In addition, since air-fuel ratio (hereafter, A/F) control has a major impact on emissions, a new two-A/F sensor system with A/F sensors provided both upstream and downstream of the catalyst was developed, incorporating an A/F control capable of further lowering emissions with greater robustness. This development identified the hysteresis characteristics of the O2 sensor downstream of the catalyst as an important factor affecting emissions during conventional A/F control. Subsequently, reaction analysis was carried out using sensor reaction models and by evaluating sensors under real-world operating conditions.
Journal Article

An Application of a Model-Prediction-Based Reference Modification Algorithm to Engine Air Path Control

2017-03-28
2017-01-0586
In real-world automotive control, there are many constraints to be considered. In order to explicitly treat the constraints, we introduce a model-prediction-based algorithm called a reference governor (RG). The RG generates modified references so that predicted future variables in a closed-loop system satisfy their constraints. One merit of introducing the RG is that effort required in control development and calibration would be reduced. In the preceding research work by Nakada et al., only a single reference case was considered. However, it is difficult to extend the previous work to more complicated systems with multiple references such as the air path control of a diesel engine due to interference between the boosting and exhaust gas recirculation (EGR) systems. Moreover, in the air path control, multiple constraints need to be considered to ensure hardware limits. Hence, it is quite beneficial to cultivate RG methodologies to deal with multiple references and constraints.
Technical Paper

Analysis for Vibration Caused by Starter Shaft Resonance

2016-04-05
2016-01-1319
It is important for vehicle concept planning to estimate fuel economy and the influence of vehicle vibration using virtual engine specifications and a virtual vehicle frame. In our former study, we showed the 1D physical power plant model with electrical starter, battery that can predict combustion transient torque, combustion heat energy and fuel efficiency. The simulation result agreed with measured data. For idling stop system, the noise and vibration during start up is important factor for salability of the vehicle. In this paper, as an application of the 1D physical power plant model (engine model), we will show the result of analysis that is starter shaft resonance and the effect on the engine mount vibration of restarting from idle stop. First, an engine model for 3.5L 6cyl NA engine was developed by energy-based model using VHDL-AMS. Here, VHDL-AMS is modeling language registered in IEC international standard (IEC61691-6) to realize multi physics on 1D simulation.
Journal Article

Development of Fracture Model for Laser Screw Welding

2016-04-05
2016-01-1344
This paper describes the development of a fracture finite element (FE) model for laser screw welding (LSW) and validation of the model with experimental results. LSW was developed and introduced to production vehicles by Toyota Motor Corporation in 2013. LSW offers superb advantages such as increased productivity and short pitch welding. Although the authors had previously developed fracture FE models for conventional resistance spot welding (RSW), a fracture model for LSW has not been developed. To develop this fracture model, many comprehensive experiments were conducted. The results revealed that LSW had twice as many variations in fracture modes compared to RSW. Moreover, fracture mode bifurcations were also found to result from differences in clearance between welded plates. In order to analyze LSW fracture phenomena, detailed FE models using fine hexahedral elements were developed.
Journal Article

Application Study of Nonlinear Viscoelastic Constitutive Model for Dynamic Behavior of Suspension Arm Bushing

2016-04-05
2016-01-1375
Ride quality is an important purchasing consideration for consumers. It is typically defined in terms of noise, vibration and harshness. These phenomena are a result of vibrations caused at the engine/powertrain and from the road surface, which are transmitted to the passenger cabin. To minimize such vibrations, rubber parts are used extensively at mounting points for the cabin, such as engine mountings and suspension bushings. The vehicle development process increasingly requires performance testing, including rubber parts using CAE, prior to prototype evaluation. This in turn requires a rubber material model that can accurately describe dynamic characteristics of rubber components, particularly frequency and amplitude dependency.
Technical Paper

Fatigue Life Prediction Method for Laser Screw Welds in Automotive Structures

2016-04-05
2016-01-0394
This paper describes the development of a fatigue life prediction method for Laser Screw Welding (LSW). Fatigue life prediction is used to assess the durability of automotive structures in the early design stages in order to shorten the vehicle development time. The LSW technology is a spot-type joining method similar to resistance spot welding (RSW), and has been developed and applied to body-inwhite structures in recent years. LSW can join metal panels even when a clearance exists between the panels. However, as a result of this favorable clearance-allowance feature of LSW, a concave shape may occur at the nugget part of the joint. These LSW geometric features, the concavity of nuggets and the clearance between panels, are thought to affect the local stiffness behavior of the joint. Therefore, while assessing the fatigue life of LSW, it is essential to estimate the influence of these factors adequately for the representation of the local stiffness behavior of the joint.
Journal Article

Development of CFD Inverse Analysis Technology Using the Transient Adjoint Method and Its Application to Engine In-Cylinder Flow

2016-04-05
2016-01-0607
Conventional CFD-based shape optimization technology that uses parametric shape modification and optimal solutions searching algorithms has the two problems: (1) outcome of optimized shapes depend on the selection of design parameters made by the designer, and (2) high computational costs. To resolve those problems, two innovative inverse analysis technologies based on the Adjoint Method were developed in previous study: surface geometry deformation sensitivity analysis to identify the locations to be modified, and topology optimization to generate an optimal shape for maximizing the cost function in the constrained design space. However, these technologies are only applicable to steady flows. Since most flows in a vehicle (such as engine in-cylinder flow) are transient, a practical technology for surface geometry sensitivity analysis has been developed based on the Transient Adjoint Method.
Journal Article

Reduction of Heat Loss and Improvement of Thermal Efficiency by Application of “Temperature Swing” Insulation to Direct-Injection Diesel Engines

2016-04-05
2016-01-0661
The reduction of the heat loss from the in-cylinder gas to the combustion chamber wall is one of the key technologies for improving the thermal efficiency of internal combustion engines. This paper describes an experimental verification of the “temperature swing” insulation concept, whereby the surface temperature of the combustion chamber wall follows that of the transient gas. First, we focus on the development of “temperature swing” insulation materials and structures with the thermo-physical properties of low thermal conductivity and low volumetric heat capacity. Heat flux measurements for the developed insulation coating show that a new insulation material formed from silica-reinforced porous anodized aluminum (SiRPA) offers both heat-rejecting properties and reliability in an internal combustion engine. Furthermore, a laser-induced phosphorescence technique was used to verify the temporal changes in the surface temperature of the developed insulation coating.
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