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Due to reciprocating nature of IC engine, flow physics in intake manifold is complex and has significant effect on volumetric efficiency. Variable length intake manifold technology offers potential for improving engine performance. This paper therefore investigated effect of intake length on volumetric efficiency for wider range of engine speeds. For this purpose 1-D thermodynamic engine model of a single cylinder 611cc standard CFR engine capable of predicting pressure waves in the intake was developed. For validation, pressure waves were predicted at two different locations on intake manifold and compared against test data. This model was used to predict volumetric efficiency for different intake lengths and engine speeds. Volumetric efficiency was found to be a function of both engine speed and intake length, more so at higher engine speeds. Frequency analysis of intake pressure waves during suction stroke and intake valve closed phase was carried out separately.

Future emission limits for off-highway application engines need advanced power train solutions to meet stringent emissions legislation, whilst meeting customer requirements and minimizing engineering costs. Development of diesel engines for off-highway application for different power segments need different intake port design solutions to optimise in-cylinder flow structure for efficient combustion. With adaptation of low pressure mechanical fuel injection system, intake port development becomes an important stage for reduction of emission formation at the source and improvement in fuel economy. In this paper, intake port design and development process is elaborated for two different power ratings of 75 hp and 120 hp of off-highway engine. 2-valve and 4-valve configurations are deployed for the same cylinder bore size.

Engine in-cylinder flow structure governs the combustion process and directly influences emission formation and fuel consumption at the source. In naturally aspirated DI diesel engine, combustion process coupled with low pressure mechanical fuel injection systems set different requirements for inlet port performance. In-cylinder swirl needs to be optimized for efficient combustion to meet emission levels and fuel consumption targets. Thus, intake port design optimization process becomes a vital requirement. In the present paper intake port design optimization is carried out for single cylinder naturally aspirated engine using mechanical fuel injection systems. The objective is to investigate in-cylinder flow field developed by intake port designs, study the effects of geometrical details of various port cross sections on flow velocity and pressure fields and establish a relationship with intake port performance parameters i.e. swirl and flow coefficient.