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Development of High-Efficiency Rotary Engines

In this presentation, we will explain how the traditional Miller Cycle - which has its limitations in the traditional four-stroke, Otto Cycle engine provides new opportunities for greater fuel efficiency gains and engine downsizing when incorporated in a split-cycle combustion process. Results will also be shared from studies showing how these implementations can provide both significant drops in fuel consumption and increases in power when incorporated into some of today's most economic vehicles. Presenter Stephen Scuderi, Scuderi Group LLC

Procedure for Mapping Fuel Consumption for small spark ignited engines

The purpose of this SAE Standard is to provide a standardized test procedure for measuring the fuel consumption of spark ignited engines in the range of 225-999cc used in the consumer and commercial turf industry. The load points and associated fuel consumption rates will be measured as the engine operates on the engine speed governor, reflecting how the user will operate the equipment. The fuel consumption calculated in gallons of useage per hour will be derived from a specified engine speed and load map to be communicated universally to end users.
Technical Paper

LPG and Prechamber as Enabler for Highly Performant and Efficient Combustion Processes Under Stoichiometric Conditions

The European Union has defined legally binding CO2-fleet targets for new cars until 2030. Therefore, improvement of fuel economy and carbon dioxide emission reduction is becoming one of the most important issues for the car manufacturers. Today’s conventional car powertrain systems are reaching their technical limits and will not be able to meet future CO2 targets without further improvement in combustion efficiency, using low carbon fuels (LCF), and at least mild electrification. This paper demonstrates a highly efficient and performant combustion engine concept with a passive pre-chamber spark plug, operating at stoichiometric conditions and powered with liquefied petroleum gas (LPG). Even from fossil origin, LPG features many advantages such as low carbon/hydrogen ratio, low price and broad availability. In future, it can be produced from renewables and it is in liquid state under relatively low pressures, allowing the use of conventional injection and fuel supply components.
Technical Paper

Powertrain Friction Reduction by Synergistic Optimization of the Cylinder Bore Surface and Lubricant Part 1: Basic Modelling

The piston assembly is the major source of tribological inefficiencies among the engine components and is responsible for about 50% of the total engine friction losses, making such a system the main target element for developing low-friction technologies. Being a reciprocating system, the piston assembly can operate in boundary, mixed and hydrodynamic lubrication regimes. Computer simulations were used to investigate the synergistic effect between low viscosity oils and cylinder bore finishes on friction reduction of passenger car internal combustion engines. First, the Reynolds equation and the Greenwood & Tripp model were used to investigating the hydrodynamic and asperity contact pressures in the top piston ring. The classical Reynolds works well for barrel-shaped profiles and relatively thick oil film thickness but has limitations for predicting the lubrication behavior of flat parallel surfaces, such as those of Oil Control Ring (OCR) outer lands.
Technical Paper

Powertrain Friction Reduction by Synergistic Optimization of Cylinder Bore Surface and Lubricant - Part 2: Engine Tribology Simulations and Tests

In the present work, a system approach to the tribological optimization of passenger car engines is demonstrated. Experimental data and simulation results are presented to demonstrate the role of surface specifications, ring pack, and lubricant on the piston/bore tribology. The importance of in-design “pairing” of low-viscosity motor oils with the ring pack and the cylinder bore characteristics in order to achieve maximum reduction in GHG emissions and improvement in fuel economy without sacrificing the endurance is elucidated. Earlier motored friction data for two different gasoline engines - Ford Duratec and Mercedes Benz M133 - using motor oils of different viscosity grades are now rationalized using AVL EXCITE® piston/bore tribology simulations. The main difference between the engines was the cylinder bore surface: honed cast iron vs thermally sprayed, and the valve train type: direct-acting mechanical bucket (DAMB) vs roller finger follower (RFF).
Technical Paper

The Effects of the Specific Material Selection on the Structural Behaviour of the Piston-Liner Coupling of a High Performance Engine

The materials commonly employed in the automotive industry are various and depend on the specific application field. For what concern the internal combustion engines the choice is guided by the thermomechanical performance required, technological constraints and production costs. Actually, for high-performance engines, steel and aluminium are the most common materials selected for the piston and the cylinder liner manufacturing. This study analyses the effect of possible material choice on the interaction between piston and cylinder liner, via Finite Element analyses. A motorcycle engine is investigated considering two possible pistons: one (standard) made of aluminium and one made of steel. Similarly, two possible cylinder liners are considered, the original one made of aluminium and a different version made of steel obtained by simply thinning the aluminium component in order to obtain two structurally equivalent components.
Technical Paper

Work Extraction Efficiency in a Series Hybrid Opposed Piston Engine

This work investigates the development of a novel series hybrid architecture utilizing a single cylinder opposed piston engine. The opposed piston engine presents unique benefits in a hybrid architecture such as its lower heat transfer due to a favorable surface area to volume ratio and lack of a cylinder head, as well as the thermodynamic benefits of two stroke operation with uniflow scavenging. A particular focus of this effort is the work extraction efficiency of two design concepts. The first design concept utilizes a geartrain to couple the crankshafts of the engine in a conventional manner, providing a single power take-off for coupling to an electric motor/generator. In this design, the large inertia of the geartrain dampens the speed fluctuation of the single cylinder engine, reducing the peak torque required to for the electric machine. However, the friction losses caused by the geartrain limit the maximum work extraction efficiency.
Technical Paper

Fuel Economy Engine Oils: Scientific Rationale and Controversies

Since a significant part of energy losses in the internal combustion engine comes from viscous dissipation, the trend has shifted toward low-viscosity oils from SAE 40 and 50 in the 1960s-1980s to current SAE 20 and lower viscosity grades. Use of low viscosity engine oils significantly reduces energy losses in the main bearing and piston/bore systems, while tribological stresses on the valvetrain - especially in flat-tappet cammed engines - may increase. This makes a strong argument for deploying new classes of friction modifiers and antiwear additives. However, development of a balanced formulation is not as straightforward as it appears, and numerous pitfalls may be encountered due to additive interactions. Another serious problem is that the definition of “fuel-economy engine oil” is rather vague, as it depends on choice of reference oil. Nowadays, the assessment of fuel economy is often based on the Sequence VIE or VIF tests using a 2012 3.6L GM V6 gasoline engine.
Technical Paper

What Are the Barriers Against Brake Thermal Efficiency beyond 55% for HD Diesel Engines?

This study focused on the technology integration to aim beyond 60% indicated thermal efficiency (ITE) with a single-cylinder heavy-duty diesel engine as an alternative to achieve 55% brake thermal efficiency (BTE) with multiple-cylinder engines. Technology assessment was initially carried out by means of a simple chart of showing ITE and exhaust heat loss as functions of cooling loss and heat conversion efficiency into indicated work. The proposed compression ratio (28:1), excess air ratio and new ideal thermodynamic cycle were then determined by a simple cycle calculation. Except for peak cylinder pressure constraint for each engine, the technical barriers for further ITE improvement are mainly laid in cooling loss reduction, fuel-air mixture formation improvement, and heat release rate optimization under very high temperature and density conditions with very high compression ratio (smaller cavity volume).
Technical Paper

Characterization of Cycle-by-Cycle Variations of an Optically Accessible Heavy-Duty Diesel Engine Retrofitted to Natural Gas Spark Ignition

The combustion process in spark-ignition engines can vary considerably cycle by cycle, which may result in unstable engine operation. The phenomena amplify in natural gas (NG) spark-ignition (SI) engines due to the lower NG laminar flame speed compared to gasoline, and more so under lean burn conditions. The main goal of this study was to investigate the main sources and the characteristics of the cycle-by-cycle variation in heavy-duty compression ignition (CI) engines converted to NG SI operation. The experiments were conducted in a single-cylinder optically-accessible CI engine with a flat bowl-in piston that was converted to NG SI. The engine was operated at medium load under lean operating conditions, using pure methane as a natural gas surrogate. The CI to SI conversion was made through the addition of a low-pressure NG injector in the intake manifold and of a NG spark plug in place of the diesel injector.
Technical Paper

A Study on Prediction of Unburned Hydrocarbons in Active Pre-chamber Gas Engine: Combustion Analysis Using 3D-CFD by Considering Wall Quenching Effects

To reproduce wall quenching phenomena using 3D-CFD, a wall quenching model was constructed based on the Peclet number. The model was further integrated with the flame propagation model. Combustion analysis showed that that a large amount of unburned hydrocarbons (UHCs) remained in the piston clevis and small gaps. Furthermore, the model was capable of predicting the increase in UHC emissions when there was a delay in the ignition time. The flame front cells were plotted on Peters' premixed turbulent combustion diagram to identify transitions in the combustion states. It was found that the flame surface transitioned from corrugated flamelets through thin reaction zones to wrinkled flamelets and further to laminar flamelets, which led to wall quenching. The turbulent Reynolds number (Re) decreased rapidly due to the increase in laminar flame speed and flame thickness and the decrease in turbulent intensity and turbulent scale.
Technical Paper

Friction Calculations and Validation Measures on an External Component Test Bench of the Piston Pin Bearing under the Influence of Greater Elastic Deformation Caused by a Hydrostatic Bearing

Increasing combustion pressure, low viscosity oils, less oil supply and the increasing stress due to downsizing of internal combustion engines (ICE) lead to higher loads within the bearing. As the mechanical and tribological loads on the piston pin bearings have a direct impact on the service life and function of the overall engine system, it is necessary to develop a robust tribological design approach. Regarding the piston pin bearing of a diesel engine, this study aims to describe the effects of different parameters on a DLC-coated piston pin within the bearing. Therefore, an external engine part test rig, which applies various forces to the connecting rod and measures the torque on a driven pin, is used to carry out validation measurements. The special feature of the test bench is the way the piston is beared. For the first experiments, the piston crown is placed against a plate (plate-bearing); later, this plate-bearing is replaced by a hydrostatic bearing.
Technical Paper

Variation in Automotive Shock Absorber Damping Characteristics & Their Effects on Ride Comfort Attribute and Vehicle Yaw Response

In a Passive suspension, a shock absorber generates damping force by pressurizing the oil flow between chambers. Typically, vehicle responds with suspension deflection, which significantly depends on damping forces and suspension velocity. Tuning dampers for various roads and steering input is an iterative balancing process. In any setting, damping force w.r.t velocity is tuned for optimum ride and handling performance. Practically, to achieve a balance between the two is a tedious task as the choices & arrangements of inner parts like piston, port, valve etc., which defines the forces set up [soft / hard] are almost infinite. The objective of this paper is to measure, objectify and evaluate the performance of two such optimum setting in various ride and handling events. A passenger car set up with an optimum soft & hard suspension damping force is studied for various ride and handling sub-attributes and their conflicts are examined in detail from a performance point of view:
Technical Paper

Mathematical Modeling of a Hydrodynamic Lubrication of a Piston Skirt Considering the Deformations and Dynamics of the Piston Displacement

One of the first tasks while designing pistons is to ensure the reliable engine operation with minimal friction losses. This is possible by ensuring the liquid friction in the piston-cylinder junction during the entire operating cycle. Therefore, it is important to assess the nature of friction in the piston-cylinder conjunction. This task can be broken down into a number of interrelated subtasks: determining the characteristics of the piston lateral movement, determining the piston deformations under thermal and mechanical loads, and calculating the hydrodynamic forces acting from the side of the oil layer in the conjunction. The use of software packages that solve these problems separately and their inclusion in the iterative process will lead to huge expenditures of computing time and is difficult to implement in carrying out design optimization problems.
Technical Paper

Digital Approach for Dynamic Balancing of Three Cylinder Gasoline Engine Crank-Train

Because of ever increasing demand for more fuel efficient engines with lower manufacturing cost, compact design and lower maintenance cost, OEM’s prefer three cylinder internal combustion engine over four cylinder engine for same capacity, though customer demands NVH characteristics of a three cylinder engines to be in line with four cylinder engine. Crank-train balancing plays most vital role in NVH aspects of three cylinder engines. A three cylinder engine crankshaft with phase angle of 120 degrees poses a challenge in balancing the crank train. In three-cylinder engines, total sum of unbalanced inertia forces occurring in each cylinder will be counterbalanced among each other. However, parts of inertia forces generated at No.1 and No. 3 cylinders will cause primary and secondary resultant moments about No. 2 cylinder. Conventional method of designing a dynamically balanced crank train is time consuming and leads to rework during manufacturing.
Technical Paper

Impact of Multiple Injection Strategies on Performance and Emissions of Methanol PPC under Low Load Operation

There is growing global interest in using renewable alcohols to reduce the greenhouse gases and the reliance on conventional fossil fuels. Recent studies show that methanol combined with partially premixed combustion provide clear performance and emission benefits compared to conventional diesel diffusion combustion. Nonetheless, high unburned hydrocarbon (HC) and carbon monoxide (CO) emissions can be stated as the main PPC drawback in light load condition when using high octane fuel such as Methanol with single injection strategy. Thus, the present experimental study has been carried out to investigate the influence of multiple injection strategies on the performance and emissions with methanol fuel in partially premixed combustion. Specifically, the main objective is to reduce HC, CO and simultaneously increase the gross indicated efficiency compared to single injection strategy.
Technical Paper

Dynamic Behavior of In-Cylinder Pressure Causing Fatigue Failure of Reed Valves

Numerous studies considering interaction between refrigerant and reed valve motion in positive displacement compressors have been cited in literature. CFD and FEA simulation tools have allowed modeling of fully coupled interaction of fluids and moving parts [1]. The present paper describes a simplified model of a multi-cylinder reciprocating piston compressor and estimation of pressure surge at high compressor speeds. The results show that the delayed discharge valve opening and closing causes surge in pressures due to formation of pressure waves. For the chosen geometry and operating conditions in the present paper, the characteristic travel time of such waves is much shorter (~ 0.2ms) as compared to longer response time of reed valves (> 1ms) owing to stiffness and exhibit delayed opening due to others factors too like stiction effect. These pressure surges may exceed the fatigue limit of reed valves and cause failures.
Journal Article

Influence of Bio Diesel Fuel on Engine Oil Performance

To evaluate the influence of FAME, which has poor oxidation stability, on engine oil performance, an engine test was conducted under large volumes of fuel dilution by post-injection. The test showed that detergent consumption and polymerization of FAME were accelerated in engine oil, causing a severe deterioration in piston cleanliness and sludge protection performance of engine oil.
Journal Article

Effect of Phenolic Brake Piston Tribology on Brake Pedal Feel

Phenolic brake pistons show excellent performance for weight saving, protection against vapor lock, noise reduction, no rust, and less seal scratch. Phenolic brake pistons have been successfully used since 1974. However there has been a complex system phenomenon related with the brake pedal feel. Our recent study focused on the tribology of phenolic brake piston and its correlation to brake pedal feel. Several surface designs of phenolic brake pistons were created and evaluated using modified JASO C448 bench test station. Our testing found the friction force between a phenolic brake piston and the piston seal differs from that of a steel brake piston. Furthermore, we discovered the friction forces on a phenolic piston could be favorably altered by the surface design of the piston. In this paper, we will propose how to improve brake pedal feel using a phenolic brake piston through designing the surface condition of the brake piston.
Journal Article


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