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Technical Paper

A Basic Study on Reduction of Cylinder Block Vibrations for Small Diesel Cars

The production unit number of small diesel engine cars tends to decline except recreational vehicles in Japanese market in recent years, while the production unit number in Europe market keeps on increasing owing to the merits of the durability and the fuel consumption. The small diesel engines will have to be improved in the near future by solving major problems such as noise and vibration pollution, environmental pollution, improvement in performance of diesel engines, in order to expand the production of the engines. This paper refers to a basic study on the experimental and analytical methods for the reduction of resonant vibration in each vibration mode on some cylinder blocks of small high-speed diesel engines in rated engine speed range. Hammering test method, which is easy and useful for measuring frequency response functions, is carried out in the experiments.
Technical Paper

A Basis for Estimating Mechanical Efficiency and Life of a Diesel Engine from its Size, Load Factor and Piston Speed

Parameters like brake mean effective pressure, mean velocity of the piston, hardness of the wear surface, oil film thickness, and surface areas of critical wear parts are similar for all the diesel engines. The mean piston velocity at the rated speed is nearly the same for all the diesel engines. The mechanical efficiency normalized to an arbitrary brake mean effective pressure (bmep) is dependent on the size of the engine. The engine life seems to be proportional directly to the square of a characteristic dimension namely, cylinder bore of the engine and inversely to speed and load factor for engines varying widely in sizes and ratings.
Technical Paper

A Big Size Rapid Compression Machine for Fundamental Studies of Diesel Combustion

As a basic tool for fundamental studies on combustion and heat transfer in diesel engines, a new rapid compression machine with a cylinder bore of 200 mm was developed which can realize in it a free diesel flame in a quiescent atmosphere, a diesel flame in a swirl, and a diesel flame impinging on the wall. The piston of this machine is driven by high pressure nitrogen, and its speed is controlled by a sophisticated hydraulic system. This paper describes the details of the mechanism and performances of the machine, and presents some examples of studies conducted with this machine.
Technical Paper

A Broad-Spectrum, Non-Metallic Additive for Gasoline and Diesel Fuels: Performance in Gasoline Engines

This paper describes the performance of a single, multifunctional additive that alleviates many of the common gasoline and Diesel fuel problems. The additive has been deemed “substantially similar” by the EPA and thus may be used for bulk treatment of unleaded gasoline. Test data obtained from several independent laboratories are presented. The results show that the additive limits octane requirement increase (ORI) to an average of about 30% of that experienced when using untreated gasolines; reduces hydrocarbon emissions by the order of 10% or more; improves fuel economy approximately 1.5% - and often much more - in a variety of engines; and also reduces exhaust valve recession and combustion chamber deposits. The additive effects on Diesel engine performance and on combustion modification in both gasoline and Diesel engines will be reported later.
Technical Paper


The resonance due to the oscillation of burned gases in the combustion chamber is particularly important in DI diesel engines. This effect can be an important excitation source of the engine block during the combustion process. Experimental studies have many limitations. Among them, the difficulty of placing different pressure transducers in the combustion chamber and the high cost of operating and mounting in an experimental room, are the most relevant. Therefore additional methodologies can be of interest. In this paper a computational fluid dynamics (CFD) approach for the study of DI automotive Diesel engine resonance is presented. With this methodology it is possible to simulate the resonance phenomenon due to the auto-ignition and the combustion process by means of energy sources. During the calculation the pressure evolution is registered in different points of the domain, and this provides the relevant information about the effects of the bowl geometry on the resonance.
Journal Article

A CFD Study of Fuel Evaporation and Related Thermo-fluid Dynamics in the Inlet Manifold, Port and Cylinder of the CFR Octane Engine

Knock in Spark Ignited (SI) engines has received significant research attention historically since this phenomenon effectively restricts the compression ratio and hence the thermal efficiency of the engine. The latent heat of vaporization (LHV) of a fuel affects its knock resistance in production engines as well as affecting its Research Octane Number (RON) rating. The reason for this is that evaporative cooling of the fuel lowers in-cylinder gas temperatures resulting in reduced tendency for end-gas auto-ignition. Controlling of the fuel-air mixture temperature to 422 K at the inlet port as per the Motor Octane Number (MON) test method ensures full evaporation of the liquid fuel, and hence LHV is assumed to have little effect during this procedure. LHV therefore has a strong influence on a fuel's Octane Sensitivity (OS) - the difference between its RON and MON values.
Technical Paper

A CFD Study of a 4-Valved, Fuel Injected Two-Stroke Spark Ignition Engine

The CFD code KIVA is used in conjunction with a one-dimensional wave action program to simulate exhaust blowdown, in a study of the scavenging and combustion at different loads and constant engine speed, in a single cylinder 4 valved 2-stroke engine configuration, using in-cylinder fuel injection. Two combustion chamber geometries -- a stepped head and a pentroof, were used in this study. The stepped head geometry has a combustion chamber recessed in the cylinder head, and contains the intake valves. The vertical intake port configuration provides a well developed reversed loop flow in the engine cylinder. The pentroof combustion chamber is similar to those used in current 4 stroke engines(1)*. The computational study focuses on the effects of injector orientation, and the subsequent interaction between the fuel spray and ‘loop swirl’ of air in the engine cylinder, and on the resulting combustion characteristics and exhaust emissions.
Technical Paper


An experimental study was conducted to investigate piston-impact generated noise in diesel engines. A coherence model was used to represent the noise generating mechanisms of the engine. The model was applied to an in-line turbo-charged diesel engine. Frequency response functions were measured between the cylinder liner vibration and the engine noise, and between the combustion pressure and the engine noise. The noise coherent with piston impacts was separated from the noise coherent with combustion. Guidelines are presented showing how the results of the coherence model may be used for engine design and noise prediction.
Technical Paper

A Calculation Methodology for Cam Overlap Optimization Towards Combustion Quality at Idle in IC SI Engines

Engine stability at idle is an important factor that influences the behaviour of an I.C., S.I. engine, in terms of fuel efficiency, exhaust gas emissions and customer comfort. In particular, the increasing daily use of vehicles in urban traffic bestows more and more importance on the engine idle quality. The engine idle quality is perceived by the user as the constancy of noise tone, low vibrations level and absence of sudden speed drop, noticeable on the steering wheel, gear shift lever, and seat [1]. Combustion characteristics play an essential role on the overall engine quality level at idle. It is important to have an estimation of the engine behaviour in this condition during the engine pre-development phase. While the fluid-dynamic calculation codes mean the engine performance at full load can be predicted, but the modelling of part load and idle behaviour is very difficult.
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.
Journal Article

A Combination of Swirl Ratio and Injection Strategy to Increase Engine Efficiency

Growing awareness about CO2 emissions and their environmental implications are leading to an increase in the importance of thermal efficiency as criteria to design internal combustion engines (ICE). Heat transfer to the combustion chamber walls contributes to a decrease in the indicated efficiency. A strategy explored in this study to mitigate this efficiency loss is to promote low swirl conditions in the combustion chamber by using low swirl ratios. A decrease in swirl ratio leads to a reduction in heat transfer, but unfortunately, it can also lead to worsening of combustion development and a decrease in the gross indicated efficiency. Moreover, pumping work plays also an important role due to the effect of reduced intake restriction to generate the swirl motion. Current research evaluates the effect of a dedicated injection strategy to enhance combustion process when low swirl is used.
Technical Paper

A Combustion Chamber Designed for Minimum Engine Exhaust Emissions

Experimental work has demonstrated that spark ignition engine exhaust emissions can be controlled through basic modification of the combustion process, and that such control can be achieved without serious compromise of the efficiency of fuel utilization. The combustion process investigated in this work is designed to exploit the finite time dependence of nitric oxide formation in high temperature combustion products. Through use of a divided combustion chamber it has been possible to quench nitric oxide formation reactions so that little nitric oxide formation occurs. Further it has been possible to simultaneously promote complete oxidation of hydrocarbons and carbon monoxide in combustion products. The combustion process, therefore, results in total control of exhaust emissions.
Technical Paper

A Combustion Model for Homogeneous Charge Natural Gas Rotary Engines

In previous papers a complete simulation model of the combustion in a gasoline rotary engine has been described. This combustion model, developed at the University of Gent and UMIST (University of Manchester Institute of Science and Technology), is based on a turbulence enhancement factor for the flame in various zones of the combustion chamber. The purpose of this paper is to give a description of the modifications of the model for a homogeneous natural gas rotary engine. The real geometry of the combustion chamber is incorporated In the model. Calculations are executed for different geometries of rotary engines (especially different positions and shapes of the recess in the rotor). Different formulas of the laminar flame speed for natural gas are examined. The turbulent flame speed is calculated with a turbulence factor or with a turbulence intensity factor. A correlation between the engine conditions and the turbulence intensity is proposed.
Technical Paper

A Common Rail Injection System For High Speed Direct Injection Diesel Engines

Lucas Diesel Systems has designed a Common Rail fuel injection system for modern high speed direct injection diesel engines. The components of the system include a new high pressure pump, a rail, and injectors which accommodate a rapid control valve within the envelope of a 17 mm diameter. The injection pressure can be controlled at all engine operating conditions within the range of 150 to 1600 bar. This paper describes the major components of this system, which is designed to provide multiple injections into the combustion chamber during each engine cycle with a good control of small deliveries. In comparison with cam-driven diesel injection systems, the common rail approach needs some additional control and supervision strategies; for example, detection of small leakages due to high pressure at the needle seat throughout the engine cycle.
Journal Article

A Comparative Low Speed Pre-Ignition (LSPI) Study in Downsized SI Gasoline and CI Diesel-Methane Dual Fuel Engines

Low speed pre-ignition (LSPI) in downsized spark-ignition engines has been studied for more than a decade but no definitive explanation has been found regarding the exact sources of auto-ignition. No single mechanism can explain all the occurrences of LSPI and that each engine should be considered as a particular case supporting different conditions for auto-ignition. In a different context, dual fuel Diesel-Methane engines have been more recently studied in large to medium bore compression ignition engines. However, if Dual Fuel combustion is less knock sensitive, LSPI remains one of the main limitations of low-end torque also for dual fuel engines. Indeed, in some cases, premature ignition of CNG can be observed before the Diesel pilot injection as LSPI can classically be observed before the spark in gasoline engines. This article aims at highlighting the similarities and discrepancies between LSPI phenomena in SI gasoline and dual fuel engines.
Technical Paper

A Comparative Study Between Salt Bath and Plasma Nitrocarburizing Processes for Application in Piston Rods

The quality of the nitrocarburized layer has a decisive influence in the service life of components with pistons that work together with polymeric seals, since it interferes in the abrasion and wear mechanisms of the involved materials. Thus it is necessary to select the most adequate process to apply in a given component aiming for a quality improvement and warranty costs reduction. The literature offers a great volume of information about the different nitriding processes, but there are few reports comparing them. In this paper the salt bath and plasma processes are discussed concerning the white layer metallography, roughness and the process effect on corrosion resistance of gas spring rods manufactured with SAE 1040 steel.
Technical Paper

A Comparative Study of Knock Formation in Gasoline and Methanol Combustion Using a Multiple Spark Ignition Approach: An Optical Investigation

Engine knock is a major challenge that limits the achievement of higher engine efficiency by increasing the compression ratio of the engine. To address this issue, using a higher octane number fuel can be a potential solution to reduce or eliminate the propensity for knock and so obtain better engine performance. Methanol, a promising alternative fuel, can be produced from conventional and non-conventional energy resources, which can help reduce pollutant emissions. Methanol has a higher octane number than typically gasolines, which makes it a viable option for reducing knock intensity. This study compared the combustion characteristics of gasoline and methanol fuels in an optical spark-ignition engine using multiple spark plugs. The experiment was carried out on a single-cylinder four-stroke optical engine. The researchers used a customized metal liner with four circumferential spark plugs to generate multiple flame kernels inside the combustion chamber.
Technical Paper

A Comparative Study on Influence of EIVC and LIVC on Fuel Economy of A TGDI Engine Part I: Friction Torques of Intake Cams with Different Profiles and Lifts

In order to better understand how the Atkinson cycle and the Miller cycle influence the fuel consumption at different engine speeds and loads, an investigation was conducted to compare influences of early intake valve closing (EIVC) and late intake valve closing (LIVC) on the fuel consumption of a 1.5L turbo-charged gasoline direct injection (TGDI) engine. The engine was tested with three different intake cams, covering three intake durations: 251 degCA (the base engine), 196 degCA (the Miller engine), and 274 degCA (the Atkinson engine). Compression ratios are 9.5:1 for the base engine and 11.4:1 for the Atkinson and Miller engines, achieved with piston modifications. Results of this investigation will be reported in three papers focusing respectively on characteristics of the engine friction, in-cylinder charge motions for different intake events, and combustion and fuel economy without and with EGR for the naturally aspirated mode and boost mode.
Technical Paper

A Comparison between Different Moving Grid Techniques for the Analysis of the TCC Engine under Motored Conditions

The accurate representation of Internal Combustion Engine (ICE) flows via CFD is an extremely complex task: it strongly depends on a combination of highly impacting factors, such as grid resolution (both local and global), choice of the turbulence model, numeric schemes and mesh motion technique. A well-founded choice must be made in order to avoid excessive computational cost and numerical difficulties arising from the combination of fine computational grids, high-order numeric schemes and geometrical complexity typical of ICEs. The paper focuses on the comparison between different mesh motion technologies, namely layer addition and removal, morphing/remapping and overset grids. Different grid strategies for a chosen mesh motion technology are also discussed. The performance of each mesh technology and grid strategy is evaluated in terms of accuracy and computational efficiency (stability, scalability, robustness).