A Method on Improvement of Small Two-Stroke Cycle Engine for Industrial and Farm Use (4th Report)

On Synthetical Consideration

Abstract

The purpose of this paper is to discuss synthetically on the following items for the both of the experimental and theoretical investigations of the two engines-the eccentric type and the general purpose engines-so far (see the 1st, 2nd and 3rd reports).
(A) Performances (indicated and brake mean effective pressure)
(B) Specific fuel consumption.
(C) Emission gases
(D) Efficiencies
(E) Frictinn losses
The conclusions obtained from them were as follows;
(1) For the eccentric type it was able to change the time areas of the inlet, scavenging and exhaust ports depending on its eccentric rate (ε) and its setting angle (a_A) of a crank-pin position.
By the suitable combination of ε and a_A, the delivery ratios, trapping efficiencies, relative charges, scavenging efficiencies, charging efficiencies, indicated and brake mean effective pressures increased and the quantity of HC and CO in the exhaust gases, and the specific fuel consumptions decreased. Further the NO_x quantities also increased a little with a incease of performance.
For example ε=0.108 and a_A=150deg. at 4000rpm, the indicated and brake mean effective pressure of the eccentric type engine were approximately 20 percent and 13 percent better than those of the general purpose type.
(2) Comparing the eccentric type with the general purpose type when the engine speed is high, the friction loss of gear surface was extremely increased. The losses of the others were however approximately the same (for example, the pumping work in the crankcase), or gave no influence on the performances.
(3) For the industrial and agricultural use (at 2000-4000rpm), the high powers, tow fuel consumptions and low emission gases are desired to be required, therefore the eccentric two strokecycle engine seems to be more useful.