China
Africa
Explore chapters and articles related to this topic
Automotive Trends in Asia
Published in Leslie R. Rudnick, Synthetics, Mineral Oils, and Bio-Based Lubricants, 2020
While two-stroke engines have definite advantages, such as reduced weight and size, higher power to weight ratio and fuel efficiency, fewer parts and lower cost to manufacture, compared with four-stroke engines, their main disadvantage is higher emissions. While a large number of Japanese engine manufacturers, notably Mazda, Subaru, Nissan, and Toyota, were very interested in developing low emission two-stroke engines in the late 1980s, this interest has declined markedly in recent years, due to the problem of overcoming the high emissions levels. However, the work to lower two-stroke emissions lead to the development of direct gasoline injection for four-stroke engines, so the research has had a positive outcome.
Introduction to Internal Combustion Engines
Published in K.A. Subramanian, Biofueled Reciprocating Internal Combustion Engines, 2017
A two-stroke engine is a type of internal combustion engine that completes a power cycle with every two strokes. One stroke means movement of a piston either upward or downward between TDC and BDC. Completion of a cycle in a two-stroke engine corresponds to one revolution of a flywheel (360-degree crank angle). Two-stroke engines have a higher specific power output than that of four-stroke engines, as well as relatively less numbers of moving parts and a lighter weight. The valve timing diagram of a two-stroke cycle engine is given in Figure 4.4.
Emissions Formation and Control
Published in John B. Heywood, Eran Sher, The Two-Stroke Cycle Engine, 2017
In general, the two-stroke cycle engine, relative to equivalent four-stroke engines, has the following inherent noise characteristics14: Because the firing frequency is doubled, noise generated by gas pressure waves is a greater problem because the human ear is more sensitive.The ports in two-stroke engines open more rapidly than poppet valves, so the pressure wave fronts are steeper, which increases the higher frequency components of the sound.Simple two-stroke cycle engines are designed to be light and compact, so the engine surfaces radiate noise more easily, and the space available for noise suppression devices is limited.Two-stroke engines usually employ a tuned exhaust, with a choked final outlet, to maximize the power output. This exhaust system feature eases the task of designing a silencer–muffler with minimum impact on power.A crankcase scavenging air pump produces lower intake air velocities than does the four-stroke engine’s induction of air directly into each cylinder.Due to its less effective filling of each cylinder with air, the two-stroke engine has lower peak cylinder pressures than the four-stroke. The resulting oscillating forces in major engine components are therefore lower, and so is the mechanical noise they generate.
A review of combustion control strategies in diesel HCCI engines
Published in Biofuels, 2018
Shyam Pandey, Parag Diwan, Pradeepta Kumar Sahoo, Sukrut Shrikant Thipse
HCCI was first suggested as an alternative combustion mode for two-stroke IC engines by Onishi et al. [6] in 1979. This combustion system, designated Active Thermo-Atmosphere Combustion (ATAC), differs from conventional gasoline and diesel combustion processes. The drawbacks of two-stroke engines are the high level of residuals at light loads, and the tendency of run-on combustion when the engine is stopped. Onishi and co-workers turned these deficiencies into strengths by devising a combustion mode (ATAC) that relied on both the high level of internal residuals and the high initial charge temperature. It was found that significant reductions in UHC emissions and an improvement in fuel economy was obtained by conditions that led to spontaneous ignition of the in-cylinder charge. It is believed that lower UHC emissions and lower fuel consumption, compared to conventional combustion from diesel engines, are obtained by the elimination of misfire and by regular combustion (less cycle-to-cycle fluctuation). ATAC is easily adaptable to two-stroke cycle SI for stable operation and the absence of misfiring in the engines is obtained in a wide region of the part throttle operation. The shift from the ATAC region to the ordinary SI region is easily accomplished without any problem. Stable HCCI could be achieved between low and high load limits with gasoline at a compression ratio of 7.5:1 in the engine speed range of 1000–4000 rpm.
Numerical analysis of modified crossbreed engine cycle under BS VI norms
Published in International Journal of Ambient Energy, 2022
P. V. Elumalai, M. Parathasarathy, S. Sathishkumar, M. Murugan, A. Saravanan, M. Sreenivasa Reddy, Keerty Venkata Sri Ramachandra Murthy
Here, the two-stroke engine can produce twice the torque and speed as the four-stroke engine because of its ability to complete the full cycle within two strokes of the engine operation (Choi et al. 2002). But the faster rate of operation of a two-stroke engine leads to incomplete combustion of fuel, which results in high fuel consumption with the emission of harmful gases, such as HC, NOx, CO and Sox into the atmosphere (Mavrelos and Theotokatos 2018; Ojapah et al. 2011). This reduces the overall efficiency of the engine.