Search Results

Two-stroke engine development has been occurring for many years. One of the main criteria affecting two-stoke piston-ported engine performance is scavenging,(4, 5, 10) which is the process of using the incoming fresh air charge to purge the cylinder of exhaust gasses. Among the simplest test procedures employed to model scavenging air flow is the “Jante” test, developed by Alfred Jante(1). This test was developed primarily to develop port designs for engines operating at peak power and so gives results having limited use for engines operating over a wide range. By altering the operating procedure as discussed in this paper, the Jante test can be used to provide useful information about the engine's scavenging characteristics over a wider range of engine operation. This offers a powerful tool for determining a porting design's effect on scavenging, and therefore engine performance.

The gas exchange process of the two-stroke engine is such that the flow of fresh air into the cylinder and exhaust gas out of the cylinder occur substantially together. It is therefore the case that not all of the air delivered will be trapped during this scavenge process. Extensive research has already been conducted into optimising the porting layouts of two-stroke engine cylinders. One of the techniques developed at The Queen's University of Belfast for evaluating scavenging is a unique experimental method described as the ‘single cycle scavenge test’. Although the test does not reflect the actual scavenge process in a firing engine, it is a sufficiently useful procedure to have become an industrial standard for scavenge evaluation. This paper discusses the application of that test procedure in the development of a multicylinder, externally scavenged, two-stroke automotive engine.

The mechanism of overhead valve train wear in moderate to low temperature service was studied using a modified fired V-D test and a motored V-D cam and cam-follower rig. High wear and Sow wear used oils from the fired test gave the correct relative wear in the motored test, indicating the motored test is a valid tool for studying wear mechanisms. Key factors affecting valve train wear were isolated and selectively introduced in a series of motored engine tests. Results from this study showed the expected increase in wear with a decrease in viscosity of unformulated lubricants. Added zinc diaikyldithiophosphate (ZDDP) reduced wear in a low viscosity lubricant and a used oil as anticipated. A high detergent, high wear oil, in an unused state, did not produce significant wear in the motored test even if all of the ZDDP was removed. Significant wear resulted only after exhaust gases (simulated blowby) were fed into the motored engine sump containing the high wear oil.

In this paper three evaluating parameters for cam lubrication characteristics in I.C. engine are introduced, namely the lubrication characteristic number Ns, the hydrodynamic characteristic number Nγ, and the non-dimensional lubrication characteristic number N̄s. The relations among them are deduced. From viewpoint of lubrication some basic points for the design of the cam profile are presented. The requirement for the condition Ns =0 is also proposed, i.e. (dNs /dϕ)Ns =0 ≥3mm/°. These evaluating parameters for cam lubrication characteristics of several current I.C. engines are computed, and finally some conclusions are drawn.

A method for determining the optimum location of oil-feed holes in crankshaft journals is described. The method is applied to the 92 series Detroit Diesel Allison Division (DDAD) engines. On an average, the minimum oil-film thickness of the main bearings was increased 83% by relocating the oil holes. A qualitative verification of the results was obtained by a coolant-contamination test. The revised crankshaft was used in the MY1985 production of the engine.

An axisymmetric three-dimensional model for in-cylinder processes has been applied to the predictions of wall heat transfer in a non-fired engine cylinder. Computed heat fluxes are shown for combustion chambers with a flat piston and a deep-bowl piston for swirl and no-swirl cases. The predictions compare well with existing experimental heat fluxes at several different radii on a cylinder head except in a central part. It is also shown that the predictions of surface-averaged heat flux are consistent with those obtained from empirical correlations. The effect of compression-expansion work is indicated by predicted temperature profiles and typically demonstrated by phase difference between the heat flux and the bulk-mean gas temperature. Computational discussions are given on local heat fluxes in the deep-bowl-piston combustion chamber and suggest that local heat fluxes are greatly increased by squish motion, squish-induced vortex, and swirling motion spun-up in the bowl.

The effects of the swirl level on the fresh air charge distribution is studied by using a multidimensional computer code for a uniflow type two-cycle diesel engine geometry. The flow is assumed to be axisymmetric. The inlet ports are simulated as an annular opening around the liner, and the exhaust valves are simulated as an annular slot in the cylinder head. Calculations are performed from exhaust valve opening to TDC for a large range of inlet port angles (10-30°). Results are presented in terms of velocity vector plots together with swirl velocity, and fresh charge contour plots. During the valves open period, the calculations indicate the presence of two vortices in the radial-axial flow plane as previously observed by Diwakar. The first one is near the liner wall (named as wall vortex) and the other is near the symmetry axis (named as the backflow vortex).

A new series of 15.2 liter heavy duty diesel engine has been developed and launched into production by Komatsu Ltd. The in-line 6 cylinder direct injection engine covers the power range of 184 - 368 KW (250-500PS) for versatile applications. It is characterized by extremely low fuel consumption (minimum b.s.f.c. is 189 g/KW.h), low noise and good transient performance, which were achieved by various design features such as ductile cast iron pistons, unique intake port arrangement and underframe construction. Turbocharged and turbocharged aftercooled versions are currently available, however, higher output versions incorporating air-to-air aftercooling or two-stage turbocharging are being developed. This paper describes details of the development objectives and the design features of the S(A)6D140 engines.

The performance of Direct Injection (DI) engines is strongly dependent upon the design of the piston bowl combustion chamber. Many different shapes have been used in the course of engine development during the past years, however, the interactions between the complex flow structure within the bowl, the fuel spray and combustion are not yet well understood. The recent advances in multidimensional mathematical models can help to analyse and interpret experimental results gained by engine tests. In this study, a 3-dimensional model for the simulation of flow and turbulence in engine cylinders is applied to two reentrant bowls of different bowl shapes, which contain the same bowl volume. The current version of the program does not allow the bowl and valve to be simultaneously in their true positions, and the intake stroke is therefore computed with a flat piston.

Measurements were made of the three velocity components at the exit plane of the intake valve from an internal combustion engine. The velocities were measured using hot-wire anemometry in a steady-flow rig, and an assessment was made of the effects of flow rate, valve lift, cylinder bore diameter, and inlet configuration on the velocity distribution around the intake valve. The results showed that over the range of flow rates tested, the normalized velocity profiles are independent of flow rate. At a fixed flow rate, the velocity profiles around the valve periphery are found to be strongly dependent on proximity to the cylinder head. Close to the cylinder head, the profiles are skewed but become more uniform as the distance from the cylinder head increases. In addition, the results indicate that the profiles are sensitive to the valve lift and to the proximity of the cylinder wall to the valve axis.

This paper describes the results of the three-dimensional numerical analysis of swirl behavior in the cylinders and piston cavities of reciprocating engines under motoring conditions. The generation of swirl during intake stroke has been calculated in one model engine having an off-center intake valve and a flat piston. Furthermore, in the other model engine having a piston with a cavity whose configuration has been changed variously, the decay of swirl during compression stroke has been calculated. The results show that the process of induction swirl generation varies considerably with the inflow velocity distribution around the intake valve, and that in the cases of non-axisyrametric corolla-like cavities the swirl decays much more greatly than in the cases of axisymmetric cavities.

Turbochargers are rightly blamed for disimproving the transient response of vehicle Diesel engines, but the serious effect of engine rotating inertia is often forgotten. Ultimately, a “no coolant” engine with lightweight ceramic parts may give substantial improvements by increasing exhaust gas temperature and at the same time reducing the inertia of engine and turbocharger components. The response of a turbocharger system can also be improved by adding energy to it, but so far such additions have required complex and costly sub-systems. A novel, cheap system is suggested.

A quasi-linear dynamic model for turbocharged diesel engine developed for control analysis and design is described in this paper. Linearized equations are obtained for the governor, the turbocharger, the combustion process, and the engine, taking into consideration the variation of the essential parameters over a wide range of the operating conditions. The model uses as its basis the steady state characteristics of the engine at the beginning and end of a change in input or load demand. The changes from one stale to another are characterized by linear transfer functions of either constant or variable parameters. Thus, the quasi-linear model developed, while retaining the advantages of the linearized approach, extends its capability in transient performance prediction of the engine over a broad operating range. Good agreement of computation results is obtained between the simulation model based on this quasi-linear approach and that based on the detailed thermodynamic cycle simulation.

This paper describe the metal-to-ceramic joining method which is important for building ceramic adiabatic engine and deals with the potential of pistons for use for adiabatic ceramic engine. Although various ceramic-to-metal joining methods have been developed, the chemical bonding method such as brazing and diffusion bonding is not only inferior in complex joining process and heat resistance, but also incapable of attaining the bonding strength of 196Mpa required of engineering ceramics. The ceramic-to-metal bonding attained generally by mechanical method such as staking results in the failure of ceramic bonding face due to a strong shearing force accompanied by the plastic deformation of metal. Therefore, the reduction of the shearing force between the ceramic and metal materials and the improvement of plasticity of the metal are necessary.

As a step in our continuing efforts to develop ceramic components for the internal combustion engine, we recently built and tested a 4-cylinder direct injection diesel engine of 1236 cc displacement. Pistons, cylinders, cylinder head-plates, a turbocharger wheel and piston rings were designed with FEI stress analysis and fabricated from solid silicon nitride or tinanium nitride-based cermet. The durability of ceramic components was confirmed by the test operation of a single-cylinder engine. After NDE test of every component to ensure the absence of defects (which may create premature component fracturing). a horizontally opposed 4-cylsnder engine was assembled and tested on a dynamometer. The effect of piston-cavity design and fuel-injection pressure on the engine's performance was investigated. Although remarkable improvements in performance were observed after specific changes, further design improvement is still needed.

Components manufactured in ceramic materials do not behave well under shock or vibratory input loads. A design is proposed which substantially isolates the ceramic cylinder and pistons of a Diesel engine from combustion shock inputs on the one hand and from mechanical vibration from the metal engine structure on the other hand. It is hoped that such a design will permit the use of low cost ceramic components and various bench and engine related tests for their evaluation, are described. The ultimate exploitation of a marketable ceramic based engine must depend on much lower part-costs than those currently passible.

Scatter of the structureborne component of interior noise can be as high as. 15dS for nominally identical vehicles. A hybrid analytical and experimental model of structureborne noise generation has been employed to evaluate the scatter problem, and it is shown that the essential features of structureborne noise scatter are reproduced using this technique. Structural - acoustic transfer functions may be used to characterise the nature and extent of structureborne noise scatter.

Designers of engine controllers have usually used an experimental trial-and-error approach to determine the best reference basis for compensating the engine dynamics. This paper investigates the nature of engine dynamics, in particular whether the dynamics are time based or crank-angle based. First, available time-based dynamics for a 5.7-L V8 TBI engine and a 3.1-L V6 PFI engine are reviewed. Next, transformation formulae between time based and crank-angle based dynamics are derived. Crank-angle based dynamics for the two engines are computed using these formulae and the results are evaluated relative to the time based dynamics. Lastly, the reference basis for a 2.5-L L4 TBI engine operating in the idle-speed region is examined. All dynamics, except fuel dynamics, are less varying in the crank-angle domain than in the time domain.

A closed loop lean limit control system by using engine roughness was studied. This system controls the air-fuel mixture close to optimum for fuel economy, which is a little richer mixture than lean misfire limit by measuring engine roughness using the information from engine speed signal. A magneto resistance type engine speed sensor was utilized as a roughness sensor and the engine roughness was calculated from that signal by a 12 bit micro-computer. It was found that the engine roughness correlated well with the variation of combustion on the dynamometer test. Some correlation measures to eliminate irregular fluctuations caused by load variations on the rough road driving condition or engine torque variations on the acceleration and deceleration condition of a vehicle, were applied to the micro-computer program. It was confirmed that the closed loop lean limit control system functioned satisfactorily. About 7% higher fuel economy than conventional system was obtained.

A continuing effort to develop noncontact test techniques for performing diesel engine diagnostics has led to recent advancements in sensor technology. The U.S. Army Tank Automotive Command (TACOM), working with RCA, is developing three new sensors: a pressure transducer for measuring dynamic exhaust pressure, a microwave transducer for measuring turbocharger speed, and a variable reluctance sensor for measuring internal combustion engine crankshaft speed and position. When used in conjunction with their automatic test equipment, Simplified Test Equipment (STE), these three sensors can help determine engine revolutions per minute, top dead center reference, turbocharger condition, turbocharged engine power potential, combustion chamber faults and fuel system faults.