Key Performance Indicators of Diesel Engines

There are many performance indicators for diesel engines, mainly including power performance indicators such as power, torque, speed, and economic performance indicators. Today, Dingbo Power Generator Manufacturer will first explain the knowledge of diesel engine indicators for you.

How to judge the performance of a diesel engine? In addition to considering power and economic indicators, it is necessary to comprehensively analyze and evaluate from aspects such as operational indicators, reliability, intensification indicators, compactness, and durability. Therefore, the indicators characterizing the quality of diesel engines are also multifaceted, and many indicators are mutually opposing and restricting. Engines for different purposes, different production conditions, and different usage conditions have different emphases on various performance indicators.

There are two types of power performance and economic performance indicators for diesel engines: one is based on the work done by the working medium in the cylinder on the piston, called indicated indicators. It can only evaluate the quality of the working cycle; the other is based on the net power obtained from the power output shaft of the diesel engine, called effective indicators. It can evaluate the performance of the entire diesel engine.

(1) Diesel Engine Indicated Work

The indicator work wi represents the work done by the gas in the cylinder on the piston when completing one working cycle.

(2) Mean Indicated Pressure

Mean indicated pressure pi= Wi/ Vh (Pa) represents the indicated work done per unit cylinder working volume in each working cycle; where Wi is the indicated work per cycle of the engine, J; Vh is the working volume of the engine cylinder, m³. Generally, Vh is in L and Wi is in kJ, then pi= Wi/ Vh (MPa)

Mean indicated pressure pi is an evaluation of the utilization rate of the engine cylinder working volume from the perspective of the actual cycle. The higher the pi value, the greater the indicated work generated by the same cylinder working volume and the higher the degree of cylinder working volume utilization. Therefore, it is an important indicator to measure the power performance of the engine's actual cycle.

(3) Indicated Power Ni

Indicated power Ni represents the indicated work done per unit time

Ni＝piVhin /30t（kW）

Where pi is the mean indicated pressure, MPa;

Vh is the working volume of the engine cylinder, L;

i is the number of engine cylinders;

n is the engine speed, r/min;

T is the stroke coefficient, t=4 for four-stroke engines, t=2 for two-stroke engines.

(4) Indicated Thermal Efficiency ηi

Indicated thermal efficiency is the ratio of the indicated work of the actual engine cycle to the heat consumed by fuel, i.e.

ηi＝Wi/Q1

Where W1 is the indicated work, kJ;

Q1 is the heat consumed to obtain the indicated work W; kJ.

For internal combustion engines, when the indicated power is Ni (kW) and the hourly fuel consumption is Gf (kg), according to the definition of η, it can be obtained

ηi＝3.6×10³Ni/GfHu

Where 3.6×10³ is the thermal equivalent of 1kW·h, kJ/kW·h;

gf is the engine hourly fuel consumption, kg/h;

Hu is the lower heating value of the fuel used, kJ/kg.

Indicated thermal efficiency is a measure of the effectiveness of converting heat into indicator work.

(5) Indicated Fuel Consumption Rate gi

The fuel amount required per kilowatt of indicated power per hour by the engine is called the indicated fuel consumption rate gi, i.e. gi＝1000Gf/Ni（g/kW·h）

Where Ni is the indicated power, kW;

Gf is the hourly fuel consumption rate, kg/h.

Therefore, there is the following relationship between the two economic indicators of the actual cycle in the engine cylinder: indicated thermal efficiency ηi and indicated fuel consumption rate gi: ηi＝3.6×10⁶/giHu

Guangxi Dingbo Generator Set Manufacturing Co.,Ltd. was founded in 1974 and is one of the earliest manufacturers of generators and diesel generator sets in China. If you want get more information, please feel free to send email to [email protected] we will pay highly attention on your question.