The manuscript. — Madras, India: Argonne National Labomtop. — 21 p.Abstract
This paper presents research efforts made in three different phases with the objective of improving the fuel economy of and reducing exhaust emissions from conventional, carbureted, two-stroke spark ignition (SI) engines, which are widely employed in two-wheel transportation in India. A review concerning the existing two-stroke engine technology for this application is included. In the first phase, a new scavenging system was developed and tested to reduce the loss of fresh charge through the exhaust port. In the second phase, the following measures were carried out to improve the combustion process: (i) using an in-cylinder catalyst, such as copper, chromium, and nickel, in the form of coating; (ii) providing moderate thermal insulation in the combustion chamber, either by depositing thin ceramic material or by metal inserts; (iii) developing a high-energy ignition system; and (iv) employing high-octane fuel, such as methanol, ethanol, eucalyptus oil, and orange oil, as a blending agent with gasoline. Based on the effectiveness of the above measures, an optimized design was developed in the final phase to achieve improved performance. Test results indicate that with an optimized two-stroke SI engine, the maximum percentage improvement in brake thermal efficiency is about 3 I%, together with a reduction of 3400 ppm in hydrocarbons (HC) and 3% by volume of carbon monoxide (CO) emissions over the normal engine (at 3 kW, 3000 rpm). Higher
cylinder peak pressures (3-5 bar), lower ignition delay (2-4 OCA), and shorter combustion duration (4-10 OCA) are obtained. The knock-limited power output is also enhanced by 12.7% at a high compression ratio (CR) of 9:l. The proposed modifications in the optimized design are simple, low-cost, and easy to adopt for both production and existing engines.
