This paper discusses the experimental investigation of extended expansion and thermal insulation on the performance of a diesel engine. A single cylinder naturally aspirated air-cooled diesel engine is modified to run on the concept of extended expansion (Miller cycle). In the modified engine, the expansion ratio is maintained greater than the effective compression ratio by modulating the intake valve closing time and the clearance volume. The cylinder head, valve, and the piston top are coated with partially stabilized zirconia (PSZ) for low heat rejection. Results show a significant improvement in fuel efficiency of the insulated extended expansion engine. A ratio of expansion ratio to effective compression ratio of 1.5 is found to be optimum. Copyright © 1997 Society of Automotive Engineers, Inc.

J. Nazar

K. V. Gopalakrishnan

Compression ratio (machinery)

Diesel engines

Expansion

Heat sinks

Thermal insulation

Zirconia

CLEARANCE VOLUME

EXPANSION ENGINES

Experimental investigations

INTAKE VALVE CLOSINGS

LOW HEAT REJECTION

NATURALLY ASPIRATED

PARTIALLY STABILIZED ZIRCONIA

SINGLE CYLINDERS

Engine cylinders

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Naturally Aspirated Low Heat Rejection Single Cylinder Extended Expansion (Miller Cycle) C.I. Engine

SAE Technical Papers

This paper deals mainly with the computer simulation and experimental investigations on a single cylinder, four stroke, spark ignited, extended expansion engine. The simulation procedure involves thermodynamic and global modeling techniques. Submodels for predicting gas exchange processes, heat transfer and friction are used. Two-zone model is adopted for combustion process. The combustion model predicts mass burning rate, ignition delay and combustion duration. It uses sub-models for calculating flame-front area, flame-speed and chemical equilibrium composition of ten product species. Experimentally measured valve-lift data along with suitable coefficient of discharge is used in the analysis of gas exchange process. Unburned hydrocarbons, carbon monoxide and nitric oxide emissions have also been predicted. Experiments have been conducted on a single cylinder, air cooled, four stroke, spark ignition engine. A production engine was modified to run as extended expansion engine. Late intake valve closure (LIVC) associated with variable compression ratio (VCR) concept is adopted to achieve extended expansion. Clearance volume has been altered to achieve variable compression ratio. In this technique, expansion ratio (ER) alone is varied while effective compression ratio (CR) is kept constant, thereby ER/CR ratio is altered. For extended expansion engine, ER/CR ratio ranges from 1.25 to 2 at CR of 7 and 8. Experiments were conducted at a constant rated speed of 1500 rpm. Performance and exhaust emissions have been measured at different loads and ER/CR ratios. The predicted performance and emission characteristics are compared with experimentally measured values. There is a good agreement between the two. It is observed that, for extended expansion engine with CR 8 and at one third load, there is a predicts mass burning rate, ignition delay and upto about 43% and improvement of about 21% in the brake thermal efficiency. At the same condition with CR 7, brake thermal efficiency improvement is about 33%. Also, unburned hydrocarbon emissions are reduced by about 60%. Carbon monoxide emissions are almost reduced to zero level. For the engine configuration considered, it is found that ER/CR ratio of 1.5 gives better performance compared to standard engine at both compression ratios. From the present investigations and comparisons of results, it is concluded that, the simulation software developed in this work predicts the performance and emission characteristics of extended expansion engine reasonably well. Therefore, it is argued that the developed code can be used with confidence for further parametric studies and to optimize the ER/CR ratio for the given engine configuration.

Numerical predictions and experimental investigations on extended expansion engine performance and exhaust emissions

SAE Technical Paper Series

Experimental Investigation on Extended Expansion Engine (EEE)

Adiabatic Turbocompound Engine Performance Prediction

Naturally aspirated low heat rejection single cylinder extended expansion (Miller Cycle) C.I. Engine

Journal	SAE Technical Papers
Publisher	SAE International
ISSN	01487191
Open Access	No