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How to Choose a Good Diesel Generator

Oct. 15, 2019

As a field power source and emergency power reserve, diesel generator sets are widely used in industrial and agricultural production, national defense, science and technology and daily life. So as a diesel generator distributor or dealer, how can we buy a satisfactory diesel generator? Starlight power technology teaches you how to judge and measure the performance of diesel generators from a professional point of view so as to buy products with high cost performance.

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Economic indicators

The economic indicator generally refers to the fuel consumption rate and the lubricating oil consumption rate of the diesel engine.


Fuel consumption rate


Fuel consumption rate, it is the diesel engine per kilowatt-hour consumption of fuel A in g / (kWh). The fuel consumption rate per kilowatt-hour in an indicator power meter is called the indicative fuel consumption rate, and the fuel consumption rate per kilowatt hour in an effective power meter is called the effective fuel consumption rate. The former indicates the indicator of diesel engine economy. The latter indicates the economic efficiency of a certain engine. The fuel consumption rate referred to in the diesel engine product description refers to the effective fuel consumption rate. The fuel consumption rate referred to in the diesel engine product description refers to the effective fuel consumption rate. After measuring torque me and rotational speed n, as well as fuel consumption per hour TGT (kg/h) and effective power Pe, the effective fuel consumption rate ge is obtained by the following formula.




The range of ge [g / (kW.h)] for diesel engines is as follows:


High speed diesel engine  



Low-speed diesel



lubricating oil consumption

The consumption of oil consumption per kilowatt-hour in a diesel engine is called the skid consumption rate in g / (kW h).


The g number of oil consumption per kilowatt-hour in a diesel engine is called the skid consumption rate in g / (kW h). Diesel engine lubricating oil is used continuously in the engine, the main reasons for its consumption are: when the diesel engine is in operation, the lubricating oil enters the combustion chamber through the piston or is burned by the air valve pipe flow in the gas cylinder, and the unburned oil is discharged with the exhaust gas. In addition, a portion of the lubricating oil due to atomization or evaporation in the crankcase by the crankcase vent. Diesel engine oil consumption rate is generally 0. 0. 5-4g/ (kW.h).

Dynamic performance index

The power performance index refers to the external work capacity of diesel engine, generally refers to the power, the average effective pressure, the rotational speed and the piston average speed and so on.


active power


The unit of power of a diesel engine in a unit of time is 1 kW 1 000 N ·m / s.


The work done by a diesel engine per unit time in the cylinder is called indicated power. The power extracted from the engine crankshaft is called effective power after the indicated power is subtracted from the friction loss of the internal parts, the mechanical loss of power such as the pump air torsion loss and the driving accessory loss is subtracted from the engine crankshaft.


If the crankshaft speed per minute is n and the crankshaft output effective power per second is We. the effective power of diesel generator is Pe=PI*nMe/30000(kW


Me is effective torque


Speed and average Piston Velocity

Speed diesel engine crankshaft per minute speed, expressed by r/min. The speed has great influence on the performance and structure of diesel engine, and its range is very wide. Various types of diesel engine speed range is different.


The average speed of the piston cm is constantly changing in the cylinder, which is larger in the middle of the stroke, smaller in the vicinity of the stop point, and zero at the stop point. If the engine speed n is known, the piston average speed can be calculated by the lower formula.




Mean Effective Pressure

The average effective pressure of eight is usually used to compare and evaluate the dynamic performance of various engines. It is a hypothetical pressure acting on the top of the piston, and it is the work done by the piston to move a stroke, equal to the effective work done per cycle.




i—number of cylinders

Vs-stroke capacityL

Pe—mean effective pressure MPa

n —engine speedr/min

t Stroke number of engine


So, Pe=30*t*Pe/i*Vs*n


It can be seen that Pe represents the effective power per unit cylinder working volume .Pe is an important index, which not only indicates the working cycle is good or bad, but also includes the size of mechanical loss, the higher the value of Pe is under the same conditions, The more effective work the engine outputs.


The values of Pe are generally as follows:

Non-turbocharged diesel engine is (0. 5—O.9)MPa

Turbocharged diesel engine is (0. 8—3.2)MPa


Exhaust pollution index

There is a small but very harmful amount of emissions in the exhaust of a diesel engine.

They are carbon monoxide CO, hydrocarbon HC, nitrogen oxide NO, and sulfur dioxide SO2. These combustion products pollute the environment and are harmful to human health, resulting in social pollution.


With the enhancement of environmental protection consciousness, the restriction of diesel engine exhaust pollution is becoming more and more strict. China's national standards (GB 267-87) have imposed no 2 limits on diesel engine emissions as follows:



When Pe>300kPage214g/(kW·h)NOx is limited at 29g/(kW .h)

When g=214-268g/(kW .h)NOx is limited at 14-25g(kW·h)

When ge>268g/(kW·h)NOx is limited at llg/(kW·h)

Weight and shape dimension index

The weight and shape size of diesel engine is an index to evaluate the structure compactness and metal material utilization ratio of diesel engine. Different types of diesel engines require different weights and dimensions.


Weight index

The weight index of a diesel engine is usually measured in terms of its specific mass. Specific mass (gw), also known as unit power mass, is the ratio of the net weight of diesel engine Gw to the calibrated power Pe.




The so-called net weight refers to the quality of the auxiliary equipment and auxiliary systems which do not include fuel oil, lubricating oil, cooling water and other auxiliary systems not directly installed on the internal combustion engine body.

The specific mass is related not only to the type of diesel engine, the structure, the size of accessories, but also to the materials used and manufacturing technology.

Shape dimension index

Shape dimension index, also called compactness index, is the index of compact degree of overall arrangement of diesel engine. It is usually measured by the unit volume power of a diesel engine.


The unit volume power Pv is the ratio between the calibration power Pe of the diesel engine and the external volume V of the diesel engine.

Pv=Pe/V (kW/m^3)


Among them, L, B, H is the maximum length, width and high size of diesel engine.


These are the methods of judging and measuring the performance of diesel generators, which are shared by the technical team of Jiangsu Starlight Electricity Equipments Co.,Ltd.

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