Simulation based study on improving the transient response quality of turbocharged diesel engines

Purpose: Use of fossil fuels in automotive sector is one of the primary causes of greenhouse emissions. The automotive engines need to perform at their best efficiency point to limit these emissions. Most of the quality indicators in this regard are based on near steady state global operational characteristics for engines without considering local performance. In the present study, extensive numerical simulations have been carried out covering a wide range of steady state and transient operating conditions to quantify interaction of turbocharger with engines through turbo-lag phenomena which may cause increased emissions during the load change conditions. Furthermore possible innovations have been explored to minimise turbo-lag phenomena.

Design Methodology/Approach: In this paper quality indicators have been developed to quantify the performance of turbocharged diesel engine under the transient event of rapid change in fueling rate which have been rarely investigated. The rate of fueling is changed from 40 mm3/injection to 52 mm3/injection at 1000 rpm engine speed which corresponds to normal operating condition. To improve quality of transient response, torque assistance method and reduction of inertia of compressor wheel have been used. Parametric study has been undertaken to analyze the quality indicators such as outlet pressure of the compressor and the compressor speed. The turbo-lag is quantified to obtain the close to optimal transient response of turbocharged diesel engine.

Findings: It has been shown that, with torque assist the transient response of the internal combustion engine is significantly improved. On the other hand, marginal improvement in transient response is observed by the reduction in inertia of the compressor wheel.

Research limitations/ implications: The findings indicate that turbo-lag can be minimised by providing torque assistance by active and passive means.

Practical Implications: The developed methods can be used in practice for efficient operation of vehicles.

Social Implications: The work carried out provides a way to minimise harmful emissions.

Originality/Value: The quality indicators developed provide a quantitative measure of turbo-lag phenomena and address the above mentioned problems.