Search Results

The piston slap is an important phenomenon in the engine, which governs the vibration, noise, and wear of liner surfaces. It occurs due to transverse and rotational motion of piston, which depends on clearance between piston and liner and is governed by geometry, mass and inertia properties of reciprocating parts, and gaseous loads. Piston slap is studied on single cylinder high-powered engine, which showed large vibrations and noise during the field trials. The classical methodology is used to determine secondary movement, contact forces and kinetic energy loss due to piston impact. The calculated result showed no major impact of piston on liner surfaces due to presence of hydrodynamic lubrication between two mating surfaces. The loss of kinetic energy due to the impact is of the order of 0.007 Nm, which is negligibly small.

With the upcoming stringent norms for diesel engines and continual pursuit for more and more fuel-efficient engines, it is necessary to enhance air-fuel mixing for proper combustion. The design of inlet port plays an important role in the engine performance, because the air-fuel mixing depends upon the air turbulence. Research showed that helical type inlet-port will be ideal for the engine with nominal injection pressure value less than 800-bar and thermodynamic simulation results highlighted the need of an optimum swirl number for the specimen engine. A parametric study on inlet port design has been done to achieve the optimum flow capacity.

A major task faced by engine manufacturers all over the world is to upgrade running engine designs with least possible modifications to meet next level of emission norms. This saves the precious lead-time and investments. In addition simplicity of design has to be maintained as far as possible while improving emissions. This is possible only by optimal combinations of FIE and engine. This paper describes such a cost effective up-gradation of an engine from US Tier 1 to US Tier 2 in very short time with minimal design changes. This difficult task was achieved by using latest techniques of simulations, measurements and concurrent engineering. For variable speed application it is desirable to retard injection timing as speed decreases, to compensate gain in absolute time. For constant speed application, retardation at part load is required as more weightage is given at part loads for the emission test cycle.

Engine up rating is not unusual in these days as the need is felt for more energy output from the same volume of the cylinder. This has increased the brake mean effective pressures in the internal combustion engines. The power train components are highly loaded as the peak firing pressures are required to be on the higher side. The connecting rod of such a highly loaded engine was designed with bmep of 2.3 MPa. To overcome the initial failures of the connecting rods it was realized that the critical design review was essential. Classical calculations and FEM studies revealed the stresses in the critical sections. The failures were overcome by the improvements in the geometry of the specific zones. The machining process improvements were necessary to reduce the stress concentration at the bottom of the blind drills. To avoid the rotation of the small bearing bush the surface finish of the connecting rod, the parent bore was improved by burnishing to get better profile metal ratio.

The rate of wear of valve seats on the valve and in the cylinder head is mainly a function of the seat load and the total relative displacement velocity after seating. The problem of wear becomes severer when the valve head deflects under large firing pressures observed in modern high bmep engines. A model relating the wear rate linearly with the product of load and the relative displacement at the seat is developed. After the valve closes, superficial delamination occurs when the shear strain due to friction at the surface exceeds the plasticity limit of material. The wear is minimised by reducing the co-efficient of friction at the interface or by reducing the relative displacement. The model was validated by accelerated experiments on an actual engine running at an 18-bar bmep. Finite element analysis of the valve and the seat showed that the displacement of the valve seat could be linearly correlated with the deflection of the valve at the center.

In a multi-cylinder engine, the harmonics of pressures in different cylinders add to excite the crankshaft and other mass-elastic system in its line. The predominant component builds up the shear stress at resonances of the system, if the natural frequencies lie in the operating range. Addition of a tuning disc in the form of a rubber damper increases the order of the system by one. The nuisance frequency is substituted by two new damped frequencies. The design of rubber for operating at high temperatures and for withstanding high shear is important. The known procedure of calculations is systematically reviewed in this paper. The importance of properties of rubber is given in detail. A successful study of damping a large 8.8 litre turbocharged and aftercooled engine rated at 2200 rpm is used to demonstrate the procedure to design a rubber damper.