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Technical Paper

A Closed Cycle Simulation Model with Particular Reference to Two-Stroke Cycle Engines

A quasi-dimensional computer simulation model is presented to simulate the thermodynamic and chemical processes occurring within a spark ignition engine during compression, combustion and expansion based upon the laws of thermodynamics and the theory of equilibrium. A two-zone combustion model, with a spherically expanding flame front originating from the spark location, is applied. The flame speed is calculated by the application of a turbulent entrainment propagation model. A simplified theory for the prediction of in-cylinder charge motion is proposed which calculates the mean turbulence intensity and scale at any time during the closed cycle. It is then used to describe both heat transfer and turbulent flame propagation. The model has been designed specifically for the two-stroke cycle engine and facilitates seven of the most common combustion chamber geometries. The fundamental theory is nevertheless applicable to any four-stroke cycle engine.
Technical Paper

A Computational Investigation into the Effects of Included Spray Angle on Heavy-Duty Diesel Engine Operating Parameters

Effects of included spray angle with different injection strategies on combustion characteristics, performance and amount of pollutant emission have been computationally investigated in a common rail heavy-duty DI diesel engine. The CFD model was firstly validated with experimental data achieved from a Caterpillar 3401 diesel engine for a conventional part load condition at 1600 rev/min. Three different included spray angles (α = 145°, 105°, 90°) were studied in comparison with the traditional spray injection angle (α = 125°). The results show that spray targeting is very effective for controlling the in-cylinder mixture distributions especially when it accompanied with various injection strategies. It was found that 105° spray cone angle along with an optimized split pre- and post-Top Dead Center (TDC) injection strategy could significantly reduce NOx and soot emissions without much penalty of the fuel consumption, as compared to the wide spray angle.
Technical Paper

A Dual-Fuel Model of Flame Initiation and Propagation for Modelling Heavy-Duty Engines with the G-Equation

We propose a novel dual-fuel combustion model for simulating heavy-duty engines with the G-Equation. Dual-Fuel combustion strategies in such engines features direct injection of a high-reactivity fuel into a lean, premixed chamber which has a high resistance to autoignition. Distinct combustion modes are present: the DI fuel auto-ignites following chemical ignition delay after spray vaporization and mixing; a reactive front is formed on its surroundings; it develops into a well-structured turbulent flame, which propagates within the premixed charge. Either direct chemistry or the flame-propagation approach (G- Equation), taken alone, do not produce accurate results. The proposed Dual-Fuel model decides what regions of the combustion chamber should be simulated with either approach, according to the local flame state; and acts as a “kernel” model for the G- Equation model. Direct chemistry is run in the regions where a premixed front is not present.
Journal Article

A Multiscale Cylinder Bore Honing Pattern Lubrication Model for Improved Engine Friction

Abstract Three-dimensional patterns representing crosshatched plateau-honed cylinder bores based on two-dimensional Fast Fourier Transform (FFT) of measured surfaces were generated and used to calculate pressure flow, shear-driven flow, and shear stress factors. Later, the flow and shear stress factors obtained by numerical simulations for various surface patterns were used to calculate lubricant film thickness and friction force between piston ring and cylinder bore contact in typical diesel engine conditions using a mixed lubrication model. The effects of various crosshatch honing angles, such as 30°, 45°, and 60°, and texture heights on engine friction losses, wear, and oil consumption were discussed in detail. It is observed from numerical results that lower lubricant film thickness values are generated with higher honing angles, particularly in mixed lubrication regime where lubricant film thickness is close to the roughness level, mainly due to lower resistance to pressure flow.
Technical Paper

A Neat Methanol Direct Injection Combustion System for Heavy-Duty Applications

A combustion system has been developed to burn neat (pure) methanol in a direct-injection four-stroke-cycle engine. Primary objectives were to obtain low fuel consumption and long component life to make the engine suitable to replace heavy-duty diesel fueled engines. A glow plug was placed in a modified quiescent combustion chamber to ensure reliable methanol ignition at all engine operating conditions. The methanol engine provides thermal efficiency nearly equal to the diesel engine from which it is derived, in addition, nitrogen oxide emissions are reduced by 50 percent and exhaust smoke is negligible. Hydrocarbon emissions are still above the baseline diesel engine. Laboratory and field durability tests of over 2000 hours have been completed. Excellent cold-start capability has been established.
Technical Paper

A New Direct Injection Combustion System for Heavy-Duty Methanol Engines

For the purpose of developing direct injection heavy-duty methanol engines which surpass diesel engines in purformace, this paper first clarifies the methanol concentration around the spark plug for achieving a high ignition stability by sampling the gas near the spark plug using a sampling valve. The combustion process of methanol is then observed by the method of high-speed Schlieren photography to clarify the mode of methanol combustion. A new methanol DISC combustion system having a protrusion in the combustion chamber is devised based on such results. This study clarifies that the methanol concentration at the point of ignition for high ignition stability is in the range of 6 to 22 vol%. The methanol mixture burns by flame propagation so far as the compression ratio is on the order of 16.5.
Technical Paper

A Study of Lean Burn Pre-Chamber Concept in a Heavy Duty Engine

Due to stringent emission standards, the demand for higher efficiency engines has been unprecedentedly high in recent years. Among several existing combustion modes, pre-chamber spark ignition (PCSI) emerges to be a potential candidate for high-efficiency engines. Research on the pre-chamber concept exhibit higher indicated efficiency through lean limit extension while maintaining the combustion stability. In this study, a unique pre-chamber geometry was tested in a single-cylinder heavy-duty engine at low load lean conditions. The geometry features a narrow throat, which was designed to be packaged inside a commercial diesel injector pocket. The pre-chamber was fueled with methane while the main chamber was supplied with an ethanol/air mixture.
Technical Paper

A Study of Nox Generation Mechanism in Diesel Exhaust Gas

The authors inserted an optical fiber into the main combustion chamber of a DI engine and led the diesel flame to the outside of the chamber. They operated the engine under various conditions and investigated into the relations between the intensity of CN band spectra in the flame, the flame temperature and the Nox concentration in the exhaust gas. As the result, a certain correlation was observed between the Nox cencentration and CN spectra, but no remarkable correlation was found between Nox and flame temperature. In view of the above facts, the Nox generation is presumably related to CN, which is an intermediate product in diesel combustion flame. IN ORDER TO MAKE CLEAR the state of combustion in diesel engines, the analysis of the phenomena must be done both in the physical and in the chemical aspects.
Technical Paper

A Study of an Outline of Combustion for a Direct Injection Stratified-Charge Rotary Engine

In order to investigate the combustion process of a Direct Injection Stratified Charge Rotary Engine (DISC-RE), a statical model combustion chamber was made and 2 stroke diesel engine was used as a Rapid Compression Machine (RCM) for the purpose of fundamental study of some characteristics of DISC-RE operation. This paper present some data on air flow in the model combustion chamber, some films of fuel injection spray, combustion flame propagation, using high speed camera, and test datas of combustion characteristics. From these films, it was clarified what happen inside of the rotor pocket. Generally to take a photograph inside of combustion chamber is very difficult using actual engine, because the combustion chamber moves toward rotational direction, so, using the static combustion chamber is very effective in the study of the fundamental process.
Technical Paper

A Study on Developing MPI Hydrogen ICE over 2MPa BMEP for Medium Duty Vehicles

Hydrogen ICE can achieve carbon neutrality and is adaptable to medium and heavy-duty vehicles, for which electricity is not always a viable option. It can also be developed using high-quality conventional diesel/gasoline engine technology. Furthermore, it allows for the conversion of existing engines to hydrogen ICE, making it highly marketable. The reliability and durability of MPI hydrogen ICE is better than that of DI, and MPI has an advantage over DI in terms of cruising range because the low-pressure injection of hydrogen reduces the remaining hydrogen in the tank. Improving MPI output is, however, an important subject, and achieving this requires suppressing abnormal combustion such as pre-ignition. In this study, an inline four-cylinder 5L turbo-charged diesel engine was converted to a hydrogen engine. Hydrogen injectors were installed in the intake ports and spark plugs were installed instead of diesel fuel injectors.
Technical Paper

A Study on Improving Fuel Consumption of Heavy-Duty Diesel Engine Specifically Designed for Long-Haul Trucks on Highway

The application of high-efficiency diesel engines, hybrid systems, waste heat recovery (WHR) systems, aftertreatment systems, and advanced drivetrains were all examined as possible approaches to improve the fuel consumption of heavy-duty, long-haul commercial trucks that mainly drive on highways. In this study, the strategies that were employed in an effort to improve the fuel consumption performance of the diesel engine itself and the results of evaluating and testing the actual engine are reported.
Technical Paper

A Superalloy Low Heat Rejection Engine with Conventional Lubrication

Low heat rejection engine (LHRE) technology reduces the heat transfer from the gases in the cylinder of an internal combustion engine by insulating the walls of the combustion chamber. This technology has the potential for gains in fuel efficiency, cooling system size decrease, the use of alternative fuels, etc. Research on many experimental LHRE's has been reported in the literature. However, these engines have used ceramic material and they have two major problems that need to be overcome. They are: (1) the need for a high temperature lubrication system, and (2) brittleness of the ceramics. To overcome these limitations, a novel LHRE design has been developed in this study. In this design, a high temperature superalloy HAYNES®230™ (USN N06230)' is used instead of ceramics, and conventional low temperature lubrication can be employed. A 3.5 HP one cylinder low heat rejection Diesel engine was developed in this study and tested for 1001 hours without failure.
Technical Paper

A Visual Study of D.I. Diesel Combustion from the Under and Lateral Sides of an Engine

A high-speed photographic study is presented illustrating the influence of engine variables such as an introduced air swirl, the number of nozzle holes and the piston cavity diameter, on the combustion process in a small direct-injection (D.I.) diesel engine. The engine was modified for optical access from the under and lateral sides of the combustion chamber. This modification enabled a three-dimensional analysis of the flame motion in the engine. The swirling velocity of a flame in a combustion chamber was highest in the piston cavity, and outside the piston cavity it became lower at the piston top and at the cylinder head in that order. The swirl ratio of the flame inside the cavity radius attenuated gradually with piston descent and approached the swirl ratio outside the cavity radius, which remained approximately constant during the expansion stroke. Engine performance was improved by retarding the attenuation of the swirl motion inside the cavity radius.
Technical Paper

Air Path Design, Technical Definition and Pre-Calibration of an Ultra-Lean Hydrogen Engine Based on OD/1D Simulation

Transport sector decarbonization is a key requirement to achieve Green House Gases emissions reduction. Future regulations and the large deployment of Low Emission Zones (LEZ) will lead to deep changes in this sector. The green hydrogen appears as a promising fuel, containing no carbon. H2 Internal combustion engine (H2 ICE) offers the opportunities of quick refueling, known reliability, relative low total cost of ownership. It is based on mature manufacturing processes and tools. Hence this solution can be commercialized in a near future, offering a short term pathway to decarbonization and a H2 market growth accelerator. However, hydrogen combustion in air generates NOx emissions, which should be reduced close to zero to fulfill future requirements. The HyMot project gathers seven public and industrial partners to develop an H2 engine for Light Commercial Vehicle (LCV) application offering the same performances as the replaced Diesel Engine.
Technical Paper

An Analysis on Heat Loss of a Heavy-Duty Diesel Engine by Wall-Impinged Spray Flame Observation

Impingement of a spray flame on the periphery of the piston cavity strongly affects heat loss to the wall. The heat release rate history is also closely correlated with the indicated thermal efficiency. For further thermal efficiency improvement, it is thus necessary to understand such phenomena in state of the art diesel engines, by observation of the actual behavior of an impinging spray flame and measurement of the local temperature and flow velocity. A top-view optically accessible engine system, for which flame impingement to the cavity wall can be observed from the top (vertically), was equipped with a high speed digital camera for direct observation. Once the flame impinged on the wall, flame tip temperature decreased roughly 100K, compared to the temperature before impingement.
Technical Paper

An Application Study of Evaporative Cooling to Heavy Duty Diesel Engines

Evaporative cooling was applied to a heavy duty diesel engine to investigate the feasibility of this cooling method. Engine test results showed the following benefits of this cooling method: Reduction of the size of theradiator and cooling fan is feasible. The maximum temperature of the combustion chamber wall did not increase, though the coolant temperature rose by 20°C. The fuel consumption could be reduced especially at partial load. Engine warm-up performance was significantly improved. An oil cooler rig test was also conducted to investigate the heat transfer characteristics of the oil cooler with evaporative cooling.
Journal Article

An Experimental Investigation of Low-Soot and Soot-Free Combustion Strategies in a Heavy-Duty, Single-Cylinder, Direct-Injection, Optical Diesel Engine

High-efficiency, clean-combustion strategies for heavy-duty diesel engines are critical for meeting stringent emissions regulations and reducing the costs of aftertreatment systems that are currently required to meet these regulations. Results from previous constant-volume combustion-vessel experiments using a single jet of fuel under quiescent conditions have shown that mixing-controlled soot-free combustion (i.e., combustion where soot is not produced) is possible with #2 diesel fuel. These experiments employed small injector-orifice diameters (≺ 150 μm) and high fuel-injection pressures (≻ 200 MPa) at top-dead-center (TDC) temperatures and densities that could be achievable in modern heavy-duty diesel engines.