Multi-characteristic

Definition

Many characteristics are horizontal with speed N, with torque T _tq or average effective pressure P _me as The ordinate, draws a number of fuel consumption curves and equivalent power curves on the figure, and constitutes the engine. Any excessive air coefficient curve can be drawn as needed, such as intake pipe vacuum curve, smoke limit, and the like.

Wanner characteristics

Diesel engine typically serves as a graph method according to the load characteristic curve under various speeds; the gasoline engine is typically made by speed characteristics. Hundreds of feature maps.

Curve

(1) Convert Different speed load characteristics to average effective pressure P _ME or t _{TQ TQ TQ < / SUB> is a horizontal coordinate, and the fuel consumption rate B is the load characteristic of the ordinate, and rotates 90 ° counterclockwise.}

(2) The rotational speed value is marked with a certain scale on the abscissa of the characteristic map. The proportion of ordinate P _ME should be the same as the proportion of load characteristics P _me .

equivalent power curve

According to the formula P _e = kp _me n, can draw an equivalent power curve, is a set hyperbola.

Boundary line

Painting T _tq -n in the outer characteristic in a multi-characteristic, constituting the boundary line.

steam, diesel engine is more characteristic Compare

(1) gasoline machine: the lowest fuel consumption is high, the economic zone is small; etc. G _e line in the low speed area Convergence to large loads, indicating that the gasoline engine at low speed, low load G _E higher. Wait n _e line with the rotational speed and obliquely, etc. G _e line, so n _e must time, the higher the N, the higher the oil; n must,

(2) Diesel Engine: The lowest g _e low, economic zone width; etc. G _e line does not converge in high and low speed, change Pingtan; When N _E line extends to a high speed, when g _e is not changed.

Application Analysis of Hundreds of Features

Mental characteristic curve is essentially synthesis of all load characteristics and speed characteristic curves. It can represent the change relationship between the engine's main parameters throughout the operating range, which can determine the most economical work area of ​​the engine, and of course it can also determine the minimum area of ​​a certain discharge pollutant, and so on. During the engine parameter matching process, these optimal performance areas are all within the most common range of works, which is one of the important principles of engine performance.

From the perspective of use, on the product engine universal characteristic graph, as shown in Figure 1, it can be seen that the full-working condition and various loads and various speeds, the average is effective. Pressure P _e , power P _E , fuel consumption rate G _e and emissions, etc., can be fully determined to be the most reasonable engine The adjustment and most advantageous use range, which is very meaningful for the choice and design of the automotive chassis parameters.

For example, when the engine outputs a certain power to the car, you can find the lowest fuel consumption rate on the equivalent power line at this power, click the corresponding speed, according to the minimum fuel consumption rate of all output power values. To design a pulse ratio of the car, you can get the best economic performance, which is one of the basis for the use of automatic transmission than design choices. Of course, it can also be analyzed by a variety of characteristic curves, calculating the economics and dynamics of the whole vehicle, various slope, different speeds, thereby developing some of the ability to design modification, safe life, use, maintenance, etc. Reference data.

(1) can easily find the engine at any point (t _tq , n) working at any point (T _tq , n), B , P _me , the engine at any point (P _e , n) Working in T _tq , b, p _me and the most economical load and speed of the engine.

(2) The shape and distribution of fuel consumption curves have a great impact on engine usage economics. The innermost innermost innermost innermost fuel consumption curve is the most economic zone, the more the curve is, the worse economy.

If the oil consumption rate is long, the engine is small in the case where the engine is not changed and the speed change is large. Commonly used medium load, medium-speed operating car engine, I hope that the most economic zone is in the middle of the characteristic, and the fuel consumption rate is long.

The fuel consumption rate is long longitudinal, and the engine is small in the case where the engine changes large and the speed change is small. Engineering mechanical engine, I hope that the most economic zone is near the calibration speed, and the fuel consumption rate is longitudinally longer.