Search Results

The design and development of a new four-stroke two-cylinder diesel engine family of 1.29 litre capacity for off road are discussed. The engine is in naturally aspirated and turbocharged and intercooled versions and rated from 11.9 kW/1500 rpm to 25.7 kW/2500 rpm. The engines were tuned for air and fuel flows, air utilisation, fuel air mixing, performance and emissions at steady state at a development lab and later certified in national labs. The high altitude capability of the TCIC was checked using a model. The engines rated at less than 19 kW satisfy India Generator set and off road norms of India and Europe equivalent to USTier4 standard, and at higher ratings, standard equivalent to US Tier4-interim. In the second part of the paper, the design of coolant and oil pumps, oil cooler for TCIC engine and the piston with steel oil control ring are discussed. The higher loaded TCIC engines use fillet hardened crankshafts of chromium molybdenum steel.

Breathing flow is the sum of blowby and pumping effect by the piston reciprocating in the crankcase. In a single cylinder engine or in an engine where the volume of the crankcase changes violently due to piston motion (e.g., a two cylinder engine where the two pistons reciprocate in phase) the fluctuating air flow through the breather would be high irrespective of engine speed but for a non-return valve. Oil slobbering through the engine breather is a function of breathing rate, oil loading and separation in the breather. Experiments showed three components of the crankcase pressure: high frequency acoustics due to the blowby jets, cyclic pressure due to the change in volume, and the pressure due to the mass flow from the cylinders and to the atmosphere through the breather valve. A model for the adiabatic pulsating flow is developed using the first law of thermodynamics.

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.

A robust and cost-effective off-road engine that is economical for backhoe application is developed to meet the Indian BS-III CEV (construction equipment vehicle) standards equivalent to the US Tier-3 emissions regulation for markets where (a) advanced maintenance facilities are not available in remote areas of operation, (b) availability of the right fuel is not fully assured, (c) the initial cost of the engine is under tight control and (d) the legendary fuel economy of direct-injection diesel engines is not traded off when migrating to higher emissions standards. The highlights of the layout of the 4-cylinder 3.8-liter 56 kW diesel engine are the use of a high-pressure exhaust gas recirculation (EGR) and a proven inline mechanical fuel injection equipment that is easy to maintain and tolerant to inferior quality of fuels used inadvertently in remote areas of operation. Use of 25% EGR reduces oxides of nitrogen (NOx) formation inside the combustion chamber by 30%.

To uprate a 6-Cylinder In-line engine from 123 kW to 165 kW in power and upgrade the emission from Euro-2 to Euro-3 it was required to go for higher peak-firing pressures (PFP). The capability of Engine's Crankshaft to withstand the PFP was increased from 125 bar to 150 bar, maintaining the same cylinder centre distance. A crank-train model was used to achieve the required crankshaft strength for infinite fatigue life. The three aspects of crankshaft design, namely, crank strength, bearing selection, journal-pin lubrication and torsional vibration were considered during the design stage. The strength to withstand 150 bar PFP was achieved by increasing the crank web-thickness. To maintain the same cylinder centre distance, crankpin and main-journal lengths were reduced. Increased throw stiffness was achieved by increasing the crankpin diameter to improve crankshaft torsional behaviour.

Emission norms are introduced to limit exhaust pollutants from vehicular engines to improve and control ambient air quality. Thermodynamic simulation results showed the possibility of upgradation from Euro-2 to Euro-3 emission norms using a low pressure inline fuel injection pump. Geometric parameters of piston bowl, injection nozzle were adjusted and the combustion parameters like swirl start of injection, controlled injection and jet penetration were fine tuned to achieve the emission norms using the cost effective inline fuel injection pump. This fuel injection system is tolerant to indifferent fuel quality as it is lubricated by engine oil and the clearances within the pump do not demand exceptional lubricity or cleanliness of the fuel. The exhaust is polished off soluble organic fractions, carbon monoxide and hydrocarbons using a lightly loaded diesel oxidation catalyst that is tolerant to 500 ppm sulphur in fuel. Data from 20 engines showed emission is consistent.

To uprate from 90 kW to 135 kW in power and upgrade the emission from Euro-II to Euro-V a base 6-cylinder naturally aspirated engine was turbocharged and after-cooled, and the fuelling method was changed from Carburetion to Multi-Point Fuel Injection (MPFI). EGR is allowed to flow from the exhaust manifold to the inlet of the compressor. The EGR flow controlled by fixed orifice was used to limit thermal loading of turbocharger. The thermodynamic model was used to optimize the ignition timing and predict the engine performance over the operating range of speed and load while allowing stoichiometric combustion. Optimum turbocharger, diameter of the EGR-pipe and the throttle body size were selected based on thermodynamic simulation. The 3-way catalytic converter and the silencer at the turbine outlet were also simulated. The real engine was developed based on the simulation and the engine performance.

Estimation of the ignition delay and concentration of exhaust emissions carries great importance in engine development process. In direct injection (DI) diesel engines, ignition delay has direct effect on startability, noise and pollutant formation. Hydrocarbon (HC) emissions are mainly due to the unburnt or partially burnt fuel leaving the engine exhaust system. In the present work, correlations have been developed for ignition delay and HC emissions. Satisfactory comparison of predicted and experimental values of ignition delay and HC emission under different operating conditions for various engines, widely varying in dimensions, method of aspiration and rated speeds validated the correlations. These correlations are useful as design tools for engine development.

It is desirable for engines to produce high torque in lower speed ranges. Such conditions are encountered when vehicles climb gradients. Two techniques are compared in this paper along with their merits and demerits to improve torque of a CI engine for lower speeds. The first method increases swirl at lower speed whereas the second method uses a combined charging system to improve airflow rates. Matching of Turbocharging equipment with diesel engine throughout the operating speed range has also been discussed in this paper. Combining both methods, provides excellent torque characteristics at lower speeds without increase in smoke and other emissions. This improves driveability of the vehicles.

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.

The rate of heat release in an indirect injection engine is modelled on the lines of the observed rate in a direct injection engine. The premixed burning is assumed to take place only in the prechamber. The diffusion burning was modelled to be proportional to the modelled rate of air entrainment and available fuel. The diffusion burning is stopped in the auxiliary chamber, once all the air in it is consumed. Comparison of experimental data with the results of simulation over a wide range of speed and load was encouraging. Different engine parameters were varied and their effects on engine performance are discussed.

The absorption and desorption of fuel by cylinder lubricating oil films has been modelled using principles of mass transfer. Henry's Law for a dilute solution of fuel in oil is used to relate gas to liquid phase fuel concentrations. Mass transfer conductances in gas and liquid phases are considered, the former via use of Reynold's Analogy to engine heat transfer data, the latter through assuming molecular diffusion through an effective penetration depth of the oil film. Oxidation of desorbed fuel is assumed complete if the mean of burned gas and lubricating oil film temperatures is greater than 1100K,. Below this value the desorbed fuel is considered to contribute to hydrocarbon emissions. Comparison with engine test data corroborate the absorption/desorption hypothesis. The model indicates the equal importance of gas and liquid phase conductances.

The study of unsteady gas exchange processes in the intake and exhaust systems of an internal combustion engine is presented in this paper. A finite difference scheme is used for solving the equations defining these systems. The transient properties like the pressure, temperature and velocity in these systems are computed by the present scheme and are compared with the results obtained using the pressure measuring devices and an ultrasonic instrument which can simultaneously measure the gas temperature and velocity.